diff --git a/global/net.go b/global/net.go
index 93756ed..f8470f4 100644
--- a/global/net.go
+++ b/global/net.go
@@ -98,7 +98,7 @@ func DownloadFile(url, path string, limit int64, headers map[string]string) erro
 		req.Header.Set(k, v)
 	}
 
-	if _, ok := headers["User-Agent"]; ok {
+	if _, ok := headers["User-Agent"]; !ok {
 		req.Header["User-Agent"] = []string{UserAgent}
 	}
 	resp, err := client.Do(req)
@@ -151,7 +151,7 @@ func DownloadFileMultiThreading(url, path string, limit int64, threadCount int,
 			req.Header.Set(k, v)
 
 		}
-		if _, ok := headers["User-Agent"]; ok {
+		if _, ok := headers["User-Agent"]; !ok {
 			req.Header["User-Agent"] = []string{UserAgent}
 		}
 		req.Header.Set("range", "bytes=0-")