diff --git a/docs/docs/en.md b/docs/docs/en.md
index 6aa5f34..4aedfdb 100644
--- a/docs/docs/en.md
+++ b/docs/docs/en.md
@@ -549,7 +549,7 @@ Allow upload file extensions
 
 Allow the maximum byte to upload
 
-* **Type:** `Number`
+* **Type:** `Number | Function`
 
 * **Default:** `0`
 
@@ -558,10 +558,36 @@ Allow the maximum byte to upload
 * **Details:**
 
   `0` is equal to not limit
+  If a `Function` is given, it will be called with the `File` object passed as an argument, and it should return a `Number`
 
 * **Usage:**
   ```html
   <file-upload :size="1024 * 1024"></file-upload>
+  <!--or-->
+  <template>
+    <file-upload :size="this.calcSize"></file-upload>
+  </template>
+  <script>
+  export default {
+    methods: {
+      calcSize(file) {
+        let size = 0;
+        let mimePrefix = file.type.substr(0, file.type.indexOf('/'));
+
+        switch (mimePrefix) {
+          case 'image':
+            size = 1024 * 1024; // 1 MiB
+            break;
+          case 'video':
+            size = 1024 * 1024 * 500; // 500 MiB
+            break;
+        }
+
+        return size;
+      }
+    }
+  }
+  </script>
   ```
 
 
diff --git a/docs/docs/zh-cn.md b/docs/docs/zh-cn.md
index 80bf344..3b2733e 100644
--- a/docs/docs/zh-cn.md
+++ b/docs/docs/zh-cn.md
@@ -467,7 +467,7 @@ input标签的 `name` 属性
 
 允许上传的最大字节
 
-* **类型:** `Number`
+* **类型:** `Number | Function`
 
 * **默认值:** `0`
 
@@ -476,10 +476,36 @@ input标签的 `name` 属性
 * **详细:**
 
   `0` 等于不限制
+  如果给出了一个`Function`，它就会以作为参数传递的`File`对象被调用，并且应该返回一个`Number`
 
 * **示例:**
   ```html
   <file-upload :size="1024 * 1024"></file-upload>
+  <!--or-->
+  <template>
+    <file-upload :size="this.calcSize"></file-upload>
+  </template>
+  <script>
+  export default {
+    methods: {
+      calcSize(file) {
+        let size = 0;
+        let mimePrefix = file.type.substr(0, file.type.indexOf('/'));
+
+        switch (mimePrefix) {
+          case 'image':
+            size = 1024 * 1024; // 1 MiB
+            break;
+          case 'video':
+            size = 1024 * 1024 * 500; // 500 MiB
+            break;
+        }
+
+        return size;
+      }
+    }
+  }
+  </script>
   ```
 
 
diff --git a/src/FileUpload.vue b/src/FileUpload.vue
index 214da26..f1b4de8 100644
--- a/src/FileUpload.vue
+++ b/src/FileUpload.vue
@@ -124,7 +124,7 @@ export default {
     },
 
     size: {
-      type: Number,
+      type: [Function, Number],
       default: 0,
     },
 
@@ -763,7 +763,9 @@ export default {
       }
 
       // 大小
-      if (this.size > 0 && file.size >= 0 && file.size > this.size) {
+      let size = (typeof this.size === 'function' ? this.size(file) : this.size)
+
+      if (size > 0 && file.size >= 0 && file.size > size) {
         return Promise.reject('size')
       }