diff --git a/crmcache.go b/crmcache.go
new file mode 100644
index 0000000..c3c212a
--- /dev/null
+++ b/crmcache.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+)
+
+func crmcache(w http.ResponseWriter, r *http.Request) {
+	// if !checkSignature(r) {
+	// 	w.WriteHeader(http.StatusUnauthorized)
+	// 	fmt.Fprintf(w, "Expired or invalid link")
+	// }
+
+	v, err := url.ParseQuery(r.URL.RawQuery)
+	if err != nil {
+		w.WriteHeader(http.StatusNotFound)
+		fmt.Fprintf(w, "parse query not valid")
+		return
+	}
+	attachmentid, ok := v["a"]
+	if !ok {
+		w.WriteHeader(http.StatusNotFound)
+		fmt.Fprintf(w, "reference number is not found")
+		return
+	}
+	id := attachmentid[0]
+	path := crmcacheFileName(id)
+
+	err = crmDownloadAttachmentAs(id, path)
+
+	if err != nil {
+		w.WriteHeader(http.StatusNotFound)
+		fmt.Fprintf(w, "reference number is not right")
+	}
+
+	if isFileExist(path) {
+		http.ServeFile(w, r, path)
+		return
+	}
+
+	w.WriteHeader(http.StatusInternalServerError)
+	fmt.Fprintf(w, "cannot build reference cache")
+}
+
+func crmcacheFileName(id string) string {
+	return CRMConfig.AttachmentCache + id
+}
diff --git a/main.go b/main.go
index cf83eae..20c6304 100644
--- a/main.go
+++ b/main.go
@@ -64,6 +64,7 @@ func setupHTTPHandler() {
 	http.HandleFunc("/iapi/getAccessToken", supplyAccessToken)
 	http.HandleFunc("/iapi/createWechatQr", iapiCreateWechatQrCode)
 	http.HandleFunc("/crmpixel.png", crmpixel) //tracking pixel.
+	http.HandleFunc("/crmcache", crmcache)
 	http.ListenAndServe(":65500", nil)
 }