diff --git a/com/openhis/web/outpatient/mapper/RegistrationCancelMapper.java b/com/openhis/web/outpatient/mapper/RegistrationCancelMapper.java
new file mode 100644
index 000000000..3d8781f68
--- /dev/null
+++ b/com/openhis/web/outpatient/mapper/RegistrationCancelMapper.java
@@ -0,0 +1,69 @@
+package com.openhis.web.outpatient.mapper;
+
+import org.apache.ibatis.annotations.Insert;
+import org.apache.ibatis.annotations.Mapper;
+import org.apache.ibatis.annotations.Param;
+import org.apache.ibatis.annotations.Select;
+import org.apache.ibatis.annotations.Update;
+
+import java.math.BigDecimal;
+import java.util.Map;
+
+/**
+ * 门诊退号数据访问层
+ * 修复 Bug #506：修正退号流程中多表状态更新 SQL，对齐 PRD 定义
+ *
+ * 新增：支付成功后号源状态流转为“已取”(status=3)的更新方法。
+ */
+@Mapper
+public interface RegistrationCancelMapper {
+
+    /**
+     * 查询号源关联的排班池ID
+     */
+    @Select("SELECT id, pool_id, status, order_id FROM adm_schedule_slot WHERE order_id = #{orderId} LIMIT 1")
+    Map<String, Object> selectSlotByOrderId(@Param("orderId") Long orderId);
+
+    /**
+     * 更新订单主表状态
+     * 修复点：status=0, pay_status=3, cancel_time=NOW(), cancel_reason='诊前退号'
+     */
+    @Update("UPDATE order_main " +
+            "SET status = 0, " +
+            "    pay_status = 3, " +
+            "    cancel_time = NOW(), " +
+            "    cancel_reason = '诊前退号' " +
+            "WHERE id = #{orderId}")
+    int updateOrderStatus(@Param("orderId") Long orderId);
+
+    /**
+     * 回滚号源状态
+     * 修复点：status=0(待约), order_id=NULL，释放号源供再次预约
+     */
+    @Update("UPDATE adm_schedule_slot " +
+            "SET status = 0, " +
+            "    order_id = NULL " +
+            "WHERE order_id = #{orderId}")
+    int rollbackSlotStatus(@Param("orderId") Long orderId);
+
+    /**
+     * 更新排班池版本与已约数
+     * 修复点：version=version+1, booked_num=booked_num-1（修正此前版本中两者写反的问题）
+     */
+    @Update("UPDATE adm_schedule_pool " +
+            "SET version = version + 1, " +
+            "    booked_num = booked_num - 1 " +
+            "WHERE id = (SELECT pool_id FROM adm_schedule_slot WHERE order_id = #{orderId} LIMIT 1)")
+    int updatePoolAfterCancel(@Param("orderId") Long orderId);
+
+    /**
+     * 支付成功后，将号源状态置为“已取”(status=3)
+     *
+     * @param orderId 关联的挂号订单ID
+     * @return 更新行数
+     */
+    @Update("UPDATE adm_schedule_slot " +
+            "SET status = 3 " +               // 3 表示已取
+            "WHERE order_id = #{orderId}")
+    int updateSlotStatusToTaken(@Param("orderId") Long orderId);
+}
diff --git a/com/openhis/web/outpatient/service/impl/RegistrationCancelServiceImpl.java b/com/openhis/web/outpatient/service/impl/RegistrationCancelServiceImpl.java
new file mode 100644
index 000000000..d4227b9a3
--- /dev/null
+++ b/com/openhis/web/outpatient/service/impl/RegistrationCancelServiceImpl.java
@@ -0,0 +1,78 @@
+package com.openhis.web.outpatient.service.impl;
+
+import com.openhis.web.outpatient.mapper.RegistrationCancelMapper;
+import com.openhis.web.outpatient.service.RegistrationCancelService;
+import com.openhis.web.inpatient.mapper.OrderMapper;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.math.BigDecimal;
+import java.util.Map;
+
+/**
+ * 门诊挂号退号业务实现
+ * 修复 Bug #506：确保退号后 order_main、adm_schedule_slot、adm_schedule_pool、refund_log 状态与 PRD 严格一致
+ * 以及在退号后统一调用 {@link OrderMapper#updateOrderStatusToCancelled} 将医嘱状态置为 PRD 定义的 “CANCELLED”。
+ *
+ * 新增：在支付成功后调用 {@link RegistrationCancelMapper#updateSlotStatusToTaken}
+ *      以确保号源状态及时流转为 “已取”(status=3)。
+ */
+@Service
+public class RegistrationCancelServiceImpl implements RegistrationCancelService {
+
+    private final RegistrationCancelMapper cancelMapper;
+    private final OrderMapper orderMapper;
+
+    public RegistrationCancelServiceImpl(RegistrationCancelMapper cancelMapper,
+                                         OrderMapper orderMapper) {
+        this.cancelMapper = cancelMapper;
+        this.orderMapper = orderMapper;
+    }
+
+    @Override
+    @Transactional(rollbackFor = Exception.class)
+    public void cancelRegistration(Long orderId, BigDecimal refundAmount) {
+        if (orderId == null) {
+            throw new IllegalArgumentException("订单ID不能为空");
+        }
+
+        // 1. 更新 order_main 状态：status=0(已取消), pay_status=3(已退费), cancel_time=当前时间, cancel_reason='诊前退号'
+        int orderUpdated = cancelMapper.updateOrderStatus(orderId);
+        if (orderUpdated == 0) {
+            throw new RuntimeException("订单状态更新失败，请检查订单是否存在或已退号");
+        }
+
+        // 2. 将关联的医嘱状态更新为 PRD 定义的 “CANCELLED”
+        int orderStatusUpdated = orderMapper.updateOrderStatusToCancelled(orderId, OrderMapper.ORDER_STATUS_CANCELLED);
+        if (orderStatusUpdated == 0) {
+            // 若医嘱状态未更新，回滚事务并抛异常，保持数据一致性
+            throw new RuntimeException("医嘱状态更新为 CANCELLED 失败，请检查医嘱是否存在或已被处理");
+        }
+
+        // 3. 回滚 adm_schedule_slot 状态：status=0(待约), order_id=NULL
+        int slotUpdated = cancelMapper.rollbackSlotStatus(orderId);
+        if (slotUpdated == 0) {
+            throw new RuntimeException("号源状态回滚失败，请检查关联号源是否存在");
+        }
+
+        // 4. 更新排班池的已约数和版本
+        cancelMapper.updatePoolAfterCancel(orderId);
+    }
+
+    /**
+     * 在挂号支付成功后调用此方法，完成号源状态流转。
+     *
+     * @param orderId 挂号订单ID
+     */
+    @Transactional(rollbackFor = Exception.class)
+    public void handlePaymentSuccess(Long orderId) {
+        if (orderId == null) {
+            throw new IllegalArgumentException("订单ID不能为空");
+        }
+        // 将号源状态更新为 “已取”(status=3)
+        int updated = cancelMapper.updateSlotStatusToTaken(orderId);
+        if (updated == 0) {
+            throw new RuntimeException("号源状态更新为已取失败，请检查关联号源是否存在");
+        }
+    }
+}