diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 9a6ccbe..44a16f9 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -45,6 +45,7 @@ jobs:
         LEANCLOUD_API_SERVER: https://us.avoscloud.com
         LEANCLOUD_APP_ID: wnDg0lPt0wcYGJSiHRwHBhD4
         LEANCLOUD_APP_KEY: u9ekx9HFSFFBErWwyWHFmPDy
+        LEANCLOUD_APP_MASTER_KEY: ${{ secrets.MASTER_KEY }}
         LEANCLOUD_REGION: US
         LEANCLOUD_APP_HOST: 127.0.0.1
         LEANCLOUD_APP_PORT: 8081
diff --git a/src/LeanCloud/File.php b/src/LeanCloud/File.php
index 2918969..827a885 100644
--- a/src/LeanCloud/File.php
+++ b/src/LeanCloud/File.php
@@ -49,6 +49,7 @@ class File {
      */
     public function __construct($name, $data=null, $mimeType=null) {
         $this->_data["name"] = $name;
+        $this->_data["key"] = null;
         $this->_source       = $data;
 
         if (!$mimeType) {
@@ -136,6 +137,24 @@ public function getName() {
         return $this->get("name");
     }
 
+    /**
+     * Get key of file
+     *
+     * @return string
+     */
+    public function getKey() {
+        return $this->get("key");
+    }
+    /**
+     * Set key of file
+     *
+     * @return self
+     */
+    public function setKey($val) {
+        $this->_data["key"] = $val;
+        return $this;
+    }
+
     /**
      * Get objectId of file
      *
@@ -258,19 +277,6 @@ public function getMeta($key=null) {
         return null;
     }
 
-    /**
-     * Generate pseudo-uuid key for filename
-     *
-     * @return string
-     */
-    private static function genFileKey() {
-        $octets = array_map(function() {
-            $num = floor((1 + Client::randomFloat()) * 0x10000);
-            return substr(dechex($num), 1);
-        }, range(0, 4));
-        return implode("", $octets);
-    }
-
     /**
      * Is the file exteranl
      *
@@ -366,12 +372,13 @@ public function save() {
 
         if ($this->isExternal()) {
             $data["url"] = $this->getUrl();
-            $resp = Client::post("/files/{$this->getName()}", $data);
+            $resp = Client::post("/files", $data);
             $this->mergeAfterSave($resp);
         } else {
-            $key = static::genFileKey();
-            $key = "{$key}." . pathinfo($this->getName(), PATHINFO_EXTENSION);
-            $data["key"]    = $key;
+            $key = $this->getKey();
+            if (isset($key)) {
+                $data["key"] = $key;
+            }
             $data["__type"] = "File";
             $resp = Client::post("/fileTokens", $data);
             if (!isset($resp["token"])) {
@@ -401,6 +408,7 @@ public function save() {
                     unset($resp[$k]);
                 }
             }
+
             $this->mergeAfterSave($resp);
         }
     }
diff --git a/test/FileTest.php b/test/FileTest.php
index 52754f3..ba12cbf 100644
--- a/test/FileTest.php
+++ b/test/FileTest.php
@@ -41,8 +41,10 @@ public function testCreateWithLocalFile() {
 
     public function testSaveTextFile() {
         $file = File::createWithData("test.txt", "Hello World!");
+        $this->assertNull($file->getKey());
         $file->save();
         $this->assertNotEmpty($file->getObjectId());
+        $this->assertNotEmpty($file->getKey());
         $this->assertNotEmpty($file->getUrl());
         $this->assertNotEmpty($file->getName());
         $this->assertEquals("text/plain", $file->getMimeType());
@@ -63,6 +65,27 @@ public function testSaveUTF8TextFile() {
         $file->destroy();
     }
 
+    public function testSaveWithSpecifiedKeyWithoutMasterKey() {
+        $file = File::createWithData("test.txt", "Hello World!");
+        $file->setKey("abc");
+        $this->assertEquals("abc", $file->getKey());
+        $unsupportedKeyError = "Unsupported file key. Please use masterKey to set file key.";
+        $this->setExpectedException("LeanCloud\CloudException", $unsupportedKeyError, 1);
+        $file->save();
+        $this->assertEmpty($file->getObjectId());
+    }
+
+    public function testSaveExternalFile() {
+        $file = File::createWithUrl("blabla.png", "https://leancloud.cn/favicon.png");
+        $file->save();
+        $this->assertNotEmpty($file->getObjectId());
+        $this->assertEquals("blabla.png", $file->getName());
+        $this->assertEquals("https://leancloud.cn/favicon.png", $file->getUrl());
+        $this->assertEquals("image/png",   $file->getMimeType());
+
+        $file->destroy();
+    }
+
     public function testFetchFile() {
         $file = File::createWithData("testFetch.txt", "你好，中国!");
         $file->save();
diff --git a/test/MasterTest.php b/test/MasterTest.php
new file mode 100644
index 0000000..f86624a
--- /dev/null
+++ b/test/MasterTest.php
@@ -0,0 +1,47 @@
+<?php
+
+use LeanCloud\LeanObject;
+use LeanCloud\Client;
+use LeanCloud\File;
+use PHPUnit\Framework\TestCase;
+
+class MasterTest extends TestCase {
+    public static function setUpBeforeClass() {
+        Client::initialize(
+            getenv("LEANCLOUD_APP_ID"),
+            getenv("LEANCLOUD_APP_KEY"),
+            getenv("LEANCLOUD_APP_MASTER_KEY"));
+        Client::useMasterKey(true);
+    }
+
+    public function testSaveWithSpecifiedKey() {
+        $file = File::createWithData("test.txt", "Hello World!");
+        $file->setKey("abc");
+        $this->assertEquals("abc", $file->getKey());
+        $file->save();
+        $this->assertNotEmpty($file->getObjectId());
+        $this->assertNotEmpty($file->getName());
+
+        $this->assertEquals("abc", $file->getKey());
+        $url = $file->getUrl();
+        $parsedUrl = parse_url($url);
+        $path = $parsedUrl["path"];
+        $oldSchoolAwsS3FileUrlPrefix = "/avos-cloud-";
+        $newAwsS3GluttonyUrlPrefix = "https://lc-gluttony";
+        if (substr($path, 0, strlen($oldSchoolAwsS3FileUrlPrefix)) === $oldSchoolAwsS3FileUrlPrefix) {
+            $splitPath = explode("/", $path, 3);
+            $this->assertEquals("abc", $splitPath[2]);
+        } else if (substr($url, 0, strlen($newAwsS3GluttonyUrlPrefix)) === $newAwsS3GluttonyUrlPrefix) {
+            $gluttonyPath = "/" + substr(getenv("LEANCLOUD_APP_KEY"), 0, 12) + "/abc";
+            $this->assertEquals($gluttonyPath, $path);
+        } else {
+            $this->assertEquals("/abc", $path);
+        }
+
+        $this->assertEquals("text/plain", $file->getMimeType());
+        $content = file_get_contents($url);
+        $this->assertEquals("Hello World!", $content);
+
+        $file->destroy();
+    }
+}
\ No newline at end of file