diff --git a/src/main/java/com/genersoft/iot/vmp/aiot/controller/AiRoiController.java b/src/main/java/com/genersoft/iot/vmp/aiot/controller/AiRoiController.java
index aa9b29ac0..1410a485a 100644
--- a/src/main/java/com/genersoft/iot/vmp/aiot/controller/AiRoiController.java
+++ b/src/main/java/com/genersoft/iot/vmp/aiot/controller/AiRoiController.java
@@ -15,6 +15,7 @@ import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 
+import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.util.List;
@@ -117,7 +118,22 @@ public class AiRoiController {
 
     @Operation(summary = "截图图片代理（服务端从 COS 下载后返回）")
     @GetMapping("/snap/image")
-    public ResponseEntity<byte[]> getSnapImage(@RequestParam String cameraCode) {
+    @RequestMapping(value = "/snap/image", method = {RequestMethod.GET, RequestMethod.HEAD})
+    public ResponseEntity<?> getSnapImage(@RequestParam String cameraCode, HttpServletRequest request) {
+        // HEAD 请求：只检查是否存在，不返回图片数据
+        if ("HEAD".equalsIgnoreCase(request.getMethod())) {
+            byte[] image = screenshotService.proxyScreenshotImage(cameraCode);
+            if (image == null || image.length == 0) {
+                return ResponseEntity.notFound().build();
+            }
+            return ResponseEntity.ok()
+                    .contentType(MediaType.IMAGE_JPEG)
+                    .contentLength(image.length)
+                    .header("Cache-Control", "public, max-age=300")
+                    .build();
+        }
+
+        // GET 请求：返回图片数据
         byte[] image = screenshotService.proxyScreenshotImage(cameraCode);
         if (image == null) {
             return ResponseEntity.notFound().build();
diff --git a/src/main/java/com/genersoft/iot/vmp/aiot/service/impl/AiScreenshotServiceImpl.java b/src/main/java/com/genersoft/iot/vmp/aiot/service/impl/AiScreenshotServiceImpl.java
index 2c22fcc9c..ddad80594 100644
--- a/src/main/java/com/genersoft/iot/vmp/aiot/service/impl/AiScreenshotServiceImpl.java
+++ b/src/main/java/com/genersoft/iot/vmp/aiot/service/impl/AiScreenshotServiceImpl.java
@@ -258,33 +258,14 @@ public class AiScreenshotServiceImpl implements IAiScreenshotService {
 
     @Override
     public byte[] proxyScreenshotImage(String cameraCode) {
-        // 1. 先查 Redis 缓存中的 presigned URL（5分钟有效）
-        String cacheJson = stringRedisTemplate.opsForValue().get(SNAP_CACHE_KEY_PREFIX + cameraCode);
-        if (cacheJson != null) {
-            try {
-                JSONObject cached = JSON.parseObject(cacheJson);
-                String cosUrl = cached.getString("url");
-                if (cosUrl != null && !cosUrl.isEmpty()) {
-                    RestTemplate restTemplate = new RestTemplate();
-                    byte[] bytes = restTemplate.getForObject(URI.create(cosUrl), byte[].class);
-                    if (bytes != null && bytes.length > 0) {
-                        log.debug("[AI截图] 代理图片(Redis缓存): cameraCode={}, size={}", cameraCode, bytes.length);
-                        return bytes;
-                    }
-                }
-            } catch (Exception e) {
-                log.warn("[AI截图] Redis 缓存 URL 下载失败，尝试 DB: {}", e.getMessage());
-            }
-        }
-
-        // 2. 查 DB 持久化的 cos_key（永不过期）
+        // 1. 查 DB 持久化的 cos_key（永不过期）- 优先直接操作 COS
         String cosKey = snapshotMapper.getCosKey(cameraCode);
         if (cosKey == null) {
-            log.warn("[AI截图] 代理图片: 无缓存也无持久化记录 cameraCode={}", cameraCode);
+            log.warn("[AI截图] 代理图片: 无持久化记录 cameraCode={}", cameraCode);
             return null;
         }
 
-        // 3. 通过 CosUtil 直接生成 presigned URL（无需调 FastAPI）
+        // 2. 通过 CosUtil 直接生成 presigned URL
         if (!cosUtil.isAvailable()) {
             log.warn("[AI截图] COS 客户端未初始化，无法生成 presigned URL");
             return null;
@@ -297,15 +278,24 @@ public class AiScreenshotServiceImpl implements IAiScreenshotService {
         }
 
         try {
-            // 4. 下载图片
+            // 3. 下载图片
             RestTemplate restTemplate = new RestTemplate();
             byte[] imageBytes = restTemplate.getForObject(URI.create(presignedUrl), byte[].class);
 
-            // 5. 更新 Redis 缓存（加速后续请求）
-            if (imageBytes != null && imageBytes.length > 0) {
-                writeCache(cameraCode, presignedUrl);
-                log.debug("[AI截图] 代理图片(DB→COS): cameraCode={}, size={}", cameraCode, imageBytes.length);
+            if (imageBytes == null || imageBytes.length == 0) {
+                log.error("[AI截图] 下载图片为空: cameraCode={}, cosKey={}", cameraCode, cosKey);
+                return null;
             }
+
+            // 验证是否为有效的 JPEG 图片（检查魔数）
+            if (imageBytes.length < 2 || (imageBytes[0] & 0xFF) != 0xFF || (imageBytes[1] & 0xFF) != 0xD8) {
+                log.error("[AI截图] 下载的数据不是有效的JPEG: cameraCode={}, size={}", cameraCode, imageBytes.length);
+                return null;
+            }
+
+            // 4. 更新 Redis 缓存（加速后续请求）
+            writeCache(cameraCode, presignedUrl);
+            log.debug("[AI截图] 代理图片成功: cameraCode={}, size={}", cameraCode, imageBytes.length);
             return imageBytes;
         } catch (Exception e) {
             log.error("[AI截图] 通过 DB cos_key 下载图片失败: cameraCode={}, cosKey={}, error={}",