diff --git a/package.json b/package.json
index 09701a9..9e99a22 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@bytedo/fetch",
-  "version": "2.1.7",
+  "version": "2.1.8",
   "description": "全新的ajax封装。分2个版本, 一个基于XMLHttpRequest, 一个基于window.fetch",
   "main": "dist/next.js",
   "files": [
diff --git a/src/lib/format.js b/src/lib/format.js
index 90a603d..7f8fb99 100644
--- a/src/lib/format.js
+++ b/src/lib/format.js
@@ -84,13 +84,17 @@ export const Format = {
   mkFormData(data) {
     let form = new FormData()
     for (let i in data) {
-      let el = data[i]
-      if (Array.isArray(el)) {
-        el.forEach(function (it) {
+      let val = data[i]
+      if (val === void 0) {
+        val = ''
+      }
+
+      if (Array.isArray(val)) {
+        val.forEach(function (it) {
           form.append(i + '[]', it)
         })
       } else {
-        form.append(i, data[i])
+        form.append(i, val)
       }
     }
     return form
@@ -105,6 +109,11 @@ export const Format = {
       if (/native code/.test(v)) {
         return
       }
+
+      if (v === void 0) {
+        v = ''
+      }
+
       let _type = getType(v)
 
       v = typeof v === 'function' ? v() : v