diff --git a/safety-cedu-service/src/main/java/org/qinan/cedu/controller/PaperExamController.java b/safety-cedu-service/src/main/java/org/qinan/cedu/controller/PaperExamController.java
index 1b337ad2..57af029d 100644
--- a/safety-cedu-service/src/main/java/org/qinan/cedu/controller/PaperExamController.java
+++ b/safety-cedu-service/src/main/java/org/qinan/cedu/controller/PaperExamController.java
@@ -3,10 +3,10 @@ package org.qinan.cedu.controller;
 import com.jjb.saas.framework.auth.utils.AuthContext;
 import io.swagger.annotations.Api;
 import io.swagger.annotations.ApiOperation;
-import io.swagger.annotations.ApiParam;
 import lombok.RequiredArgsConstructor;
 import org.qinan.cedu.model.dto.AnswerQuestionDTO;
 import org.qinan.cedu.model.dto.StartExamDTO;
+import org.qinan.cedu.model.dto.SubmitExamDTO;
 import org.qinan.cedu.model.vo.StartExamVO;
 import org.qinan.cedu.service.PaperExamService;
 import org.qinan.safetyeval.client.dto.SingleResponse;
@@ -14,7 +14,6 @@ import org.springframework.validation.annotation.Validated;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
-import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RestController;
 
 /**
@@ -53,8 +52,8 @@ public class PaperExamController {
      */
     @ApiOperation("交卷")
     @PostMapping("/submitExam")
-    public SingleResponse<Void> submitExam(@ApiParam(value = "试卷id", required = true) @RequestParam Long paperId) {
-        paperExamService.submitExam(paperId, AuthContext.getUserId());
+    public SingleResponse<Void> submitExam(@Validated @RequestBody SubmitExamDTO dto) {
+        paperExamService.submitExam(dto, AuthContext.getUserId());
         return SingleResponse.success();
     }
 }
diff --git a/safety-cedu-service/src/main/java/org/qinan/cedu/mapper/PaperExamQuestionUserMapper.java b/safety-cedu-service/src/main/java/org/qinan/cedu/mapper/PaperExamQuestionUserMapper.java
index fbbd7bbc..1c44ebd1 100644
--- a/safety-cedu-service/src/main/java/org/qinan/cedu/mapper/PaperExamQuestionUserMapper.java
+++ b/safety-cedu-service/src/main/java/org/qinan/cedu/mapper/PaperExamQuestionUserMapper.java
@@ -2,11 +2,22 @@ package org.qinan.cedu.mapper;
 
 import com.baomidou.mybatisplus.core.mapper.BaseMapper;
 import org.apache.ibatis.annotations.Mapper;
+import org.apache.ibatis.annotations.Param;
 import org.qinan.cedu.model.entity.PaperExamQuestionUserDO;
 
+import java.math.BigDecimal;
+
 /**
  * 用户试卷试题 Mapper
  */
 @Mapper
 public interface PaperExamQuestionUserMapper extends BaseMapper<PaperExamQuestionUserDO> {
+
+    /**
+     * 汇总一次考试所有试题的作答得分（数据库SUM聚合，未作答按0分计入）
+     *
+     * @param paperExamId 考试记录id
+     * @return 作答总得分（无记录时返回0）
+     */
+    BigDecimal sumAnswerScore(@Param("paperExamId") Long paperExamId);
 }
diff --git a/safety-cedu-service/src/main/java/org/qinan/cedu/model/dto/SubmitExamDTO.java b/safety-cedu-service/src/main/java/org/qinan/cedu/model/dto/SubmitExamDTO.java
new file mode 100644
index 00000000..bb5a63f8
--- /dev/null
+++ b/safety-cedu-service/src/main/java/org/qinan/cedu/model/dto/SubmitExamDTO.java
@@ -0,0 +1,19 @@
+package org.qinan.cedu.model.dto;
+
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import lombok.Data;
+
+import javax.validation.constraints.NotNull;
+
+/**
+ * 考试交卷入参
+ */
+@Data
+@ApiModel(value = "SubmitExamDTO", description = "考试交卷入参")
+public class SubmitExamDTO {
+
+    @ApiModelProperty(value = "试卷id", required = true)
+    @NotNull(message = "试卷id不能为空")
+    private Long paperId;
+}
diff --git a/safety-cedu-service/src/main/java/org/qinan/cedu/service/PaperExamService.java b/safety-cedu-service/src/main/java/org/qinan/cedu/service/PaperExamService.java
index 10cace5e..0f975574 100644
--- a/safety-cedu-service/src/main/java/org/qinan/cedu/service/PaperExamService.java
+++ b/safety-cedu-service/src/main/java/org/qinan/cedu/service/PaperExamService.java
@@ -6,6 +6,7 @@ import org.qinan.cedu.model.dto.AnswerQuestionDTO;
 import org.qinan.cedu.model.dto.PaperExamDTO;
 import org.qinan.cedu.model.dto.PaperExamPageQueryDTO;
 import org.qinan.cedu.model.dto.StartExamDTO;
+import org.qinan.cedu.model.dto.SubmitExamDTO;
 import org.qinan.cedu.model.entity.PaperExamDO;
 import org.qinan.cedu.model.vo.PaperExamVO;
 import org.qinan.cedu.model.vo.StartExamVO;
@@ -74,8 +75,8 @@ public interface PaperExamService extends IService<PaperExamDO> {
     /**
      * 交卷：汇总用户最近一次进行中考试各试题作答得分，更新考试成绩、是否通过并结束考试
      *
-     * @param paperId 试卷id
-     * @param userId  用户id
+     * @param dto    交卷入参（试卷id必填）
+     * @param userId 当前用户id
      */
-    void submitExam(Long paperId, Long userId);
+    void submitExam(SubmitExamDTO dto, Long userId);
 }
diff --git a/safety-cedu-service/src/main/java/org/qinan/cedu/service/impl/PaperExamServiceImpl.java b/safety-cedu-service/src/main/java/org/qinan/cedu/service/impl/PaperExamServiceImpl.java
index d206af74..272bf186 100644
--- a/safety-cedu-service/src/main/java/org/qinan/cedu/service/impl/PaperExamServiceImpl.java
+++ b/safety-cedu-service/src/main/java/org/qinan/cedu/service/impl/PaperExamServiceImpl.java
@@ -1,5 +1,6 @@
 package org.qinan.cedu.service.impl;
 
+import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
 import com.baomidou.mybatisplus.core.metadata.IPage;
 import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
 import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
@@ -10,12 +11,14 @@ import org.qinan.cedu.enums.AnswerStatusEnum;
 import org.qinan.cedu.enums.DeleteEnum;
 import org.qinan.cedu.enums.PaperExamStatusEnum;
 import org.qinan.cedu.mapper.PaperExamMapper;
+import org.qinan.cedu.mapper.PaperExamQuestionUserMapper;
 import org.qinan.cedu.mapper.PaperMapper;
 import org.qinan.cedu.mapper.QuestionMapper;
 import org.qinan.cedu.model.dto.AnswerQuestionDTO;
 import org.qinan.cedu.model.dto.PaperExamDTO;
 import org.qinan.cedu.model.dto.PaperExamPageQueryDTO;
 import org.qinan.cedu.model.dto.StartExamDTO;
+import org.qinan.cedu.model.dto.SubmitExamDTO;
 import org.qinan.cedu.model.entity.PaperDO;
 import org.qinan.cedu.model.entity.PaperExamDO;
 import org.qinan.cedu.model.entity.PaperExamQuestionUserDO;
@@ -36,7 +39,6 @@ import java.time.LocalDateTime;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
-import java.util.Objects;
 import java.util.stream.Collectors;
 
 /**
@@ -57,6 +59,8 @@ public class PaperExamServiceImpl extends ServiceImpl<PaperExamMapper, PaperExam
 
     private final PaperExamQuestionUserService paperExamQuestionUserService;
 
+    private final PaperExamQuestionUserMapper paperExamQuestionUserMapper;
+
     @Override
     public IPage<PaperExamVO> pageQuery(PaperExamPageQueryDTO query) {
         return this.lambdaQuery()
@@ -139,14 +143,20 @@ public class PaperExamServiceImpl extends ServiceImpl<PaperExamMapper, PaperExam
     @Override
     @Transactional(rollbackFor = Exception.class)
     public void answerQuestion(AnswerQuestionDTO dto, Long userId) {
+        // 仅查询后续用到的字段，updateById 默认忽略 null 字段，未查询字段不会被覆盖
         PaperExamQuestionUserDO questionUser = paperExamQuestionUserService.lambdaQuery()
+                .select(PaperExamQuestionUserDO::getId, PaperExamQuestionUserDO::getQuestionId,
+                        PaperExamQuestionUserDO::getQuestionScore)
                 .eq(PaperExamQuestionUserDO::getId, dto.getId())
                 .eq(PaperExamQuestionUserDO::getUserId, userId)
                 .one();
         if (questionUser == null) {
             throw new IllegalArgumentException("作答记录不存在");
         }
-        QuestionDO question = questionMapper.selectById(questionUser.getQuestionId());
+        // 仅查询判分需要的参考答案字段
+        QuestionDO question = questionMapper.selectOne(new LambdaQueryWrapper<QuestionDO>()
+                .select(QuestionDO::getAnswer, QuestionDO::getAnswerQuestionOptionIds)
+                .eq(QuestionDO::getId, questionUser.getQuestionId()));
         if (question == null) {
             throw new IllegalArgumentException("试题不存在");
         }
@@ -162,9 +172,9 @@ public class PaperExamServiceImpl extends ServiceImpl<PaperExamMapper, PaperExam
 
     @Override
     @Transactional(rollbackFor = Exception.class)
-    public void submitExam(Long paperId, Long userId) {
+    public void submitExam(SubmitExamDTO dto, Long userId) {
         PaperExamDO paperExam = this.lambdaQuery()
-                .eq(PaperExamDO::getPaperId, paperId)
+                .eq(PaperExamDO::getPaperId, dto.getPaperId())
                 .eq(PaperExamDO::getUserId, userId)
                 .eq(PaperExamDO::getPaperExamStatus, PaperExamStatusEnum.DOING.getValue())
                 .eq(PaperExamDO::getDeleteEnum, DeleteEnum.FALSE.getCode())
@@ -211,17 +221,10 @@ public class PaperExamServiceImpl extends ServiceImpl<PaperExamMapper, PaperExam
     }
 
     /**
-     * 汇总一次考试所有试题的作答得分（未作答按0分计入）
+     * 汇总一次考试所有试题的作答得分（数据库SUM聚合，未作答按0分计入）
      */
     private BigDecimal sumAnswerScore(Long paperExamId) {
-        List<PaperExamQuestionUserDO> questionUserList = paperExamQuestionUserService.lambdaQuery()
-                .eq(PaperExamQuestionUserDO::getPaperExamId, paperExamId)
-                .eq(PaperExamQuestionUserDO::getDeleteEnum, DeleteEnum.FALSE.getCode())
-                .list();
-        return questionUserList.stream()
-                .map(PaperExamQuestionUserDO::getAnswerScore)
-                .filter(Objects::nonNull)
-                .reduce(BigDecimal.ZERO, BigDecimal::add);
+        return paperExamQuestionUserMapper.sumAnswerScore(paperExamId);
     }
 
     /**
diff --git a/safety-cedu-service/src/main/resources/mapper/PaperExamQuestionUserMapper.xml b/safety-cedu-service/src/main/resources/mapper/PaperExamQuestionUserMapper.xml
new file mode 100644
index 00000000..b1001894
--- /dev/null
+++ b/safety-cedu-service/src/main/resources/mapper/PaperExamQuestionUserMapper.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
+<mapper namespace="org.qinan.cedu.mapper.PaperExamQuestionUserMapper">
+
+    <select id="sumAnswerScore" resultType="java.math.BigDecimal">
+        SELECT IFNULL(SUM(answer_score), 0)
+        FROM paper_exam_question_user
+        WHERE paper_exam_id = #{paperExamId}
+        AND delete_enum = 'false'
+    </select>
+</mapper>