diff --git a/src/Pack.php b/src/Pack.php
index cfcbad2..ea5b41a 100644
--- a/src/Pack.php
+++ b/src/Pack.php
@@ -21,7 +21,7 @@ class Pack {
     const DATA_TYPE_SAMPLE_DATA = 1;
 
     /**
-     * @var integral 包的最大长度
+     * @var integral 包的最大长度20m
      */
     static public $packageMaxLength = 1024 * 1024 * 20;