diff --git a/src/main/java/com/openhis/application/service/impl/RegistrationServiceImpl.java b/src/main/java/com/openhis/application/service/impl/RegistrationServiceImpl.java
new file mode 100644
index 000000000..3b212c444
--- /dev/null
+++ b/src/main/java/com/openhis/application/service/impl/RegistrationServiceImpl.java
@@ -0,0 +1,90 @@
+package com.openhis.application.service.impl;
+
+import com.openhis.application.domain.entity.Registration;
+import com.openhis.application.domain.entity.RegistrationDetail;
+import com.openhis.application.mapper.RegistrationMapper;
+import com.openhis.application.mapper.RegistrationDetailMapper;
+import com.openhis.application.exception.BusinessException;
+import com.openhis.application.service.RegistrationService;
+import com.openhis.application.constants.RegistrationStatus;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+/**
+ * 门诊挂号业务实现
+ *
+ * 修复 Bug #506：门诊诊前退号后，数据库多表状态值变更与 PRD 定义不符。
+ *
+ * 退号业务需要同时更新以下表的状态：
+ *   1. registration_main   → status = "CANCELLED"
+ *   2. registration_detail → status = "CANCELLED"
+ *
+ * 之前的实现只更新了 registration_main 表，导致 registration_detail
+ * 仍保持原来的 “REGISTERED” 状态，与产品需求不一致，进而在后续查询、统计
+ * 以及对账时出现数据不一致的问题。
+ *
+ * 本次修复在同一事务内统一更新两张表，并使用统一的状态常量
+ * {@link RegistrationStatus#CANCELLED}，确保所有相关记录的状态保持同步。
+ */
+@Service
+public class RegistrationServiceImpl implements RegistrationService {
+
+    private static final Logger log = LoggerFactory.getLogger(RegistrationServiceImpl.class);
+
+    private final RegistrationMapper registrationMapper;
+    private final RegistrationDetailMapper registrationDetailMapper;
+
+    public RegistrationServiceImpl(RegistrationMapper registrationMapper,
+                                   RegistrationDetailMapper registrationDetailMapper) {
+        this.registrationMapper = registrationMapper;
+        this.registrationDetailMapper = registrationDetailMapper;
+    }
+
+    /**
+     * 诊前退号
+     *
+     * @param registrationId 挂号主键
+     * @throws BusinessException 若挂号不存在或已退号
+     */
+    @Override
+    @Transactional(rollbackFor = Exception.class)
+    public void cancelRegistration(Long registrationId) {
+        // 1. 查询挂号主记录，确保存在且未退号
+        Registration registration = registrationMapper.selectByPrimaryKey(registrationId);
+        if (registration == null) {
+            log.warn("Attempt to cancel non‑existent registration, id={}", registrationId);
+            throw new BusinessException("挂号记录不存在");
+        }
+        if (RegistrationStatus.CANCELLED.equals(registration.getStatus())) {
+            log.warn("Registration already cancelled, id={}", registrationId);
+            throw new BusinessException("挂号已退号，无需重复操作");
+        }
+
+        // 2. 更新挂号主表状态
+        registration.setStatus(RegistrationStatus.CANCELLED);
+        registrationMapper.updateByPrimaryKeySelective(registration);
+        log.info("Registration main status set to CANCELLED, id={}", registrationId);
+
+        // 3. 更新挂号明细表状态（可能有多条明细）
+        List<RegistrationDetail> details = registrationDetailMapper.selectByRegistrationId(registrationId);
+        if (details != null && !details.isEmpty()) {
+            for (RegistrationDetail detail : details) {
+                detail.setStatus(RegistrationStatus.CANCELLED);
+                registrationDetailMapper.updateByPrimaryKeySelective(detail);
+            }
+            log.info("Updated {} registration detail records to CANCELLED, registrationId={}",
+                    details.size(), registrationId);
+        } else {
+            log.debug("No registration detail records found for registrationId={}", registrationId);
+        }
+
+        // 4. 业务日志（可选）
+        // auditLogService.recordCancel(registrationId, CurrentUserHolder.getUserId());
+    }
+
+    // 其它业务方法保持不变...
+}