diff --git a/Aria/src/main/java/com/arialyy/aria/core/download/ConnectionHelp.java b/Aria/src/main/java/com/arialyy/aria/core/download/ConnectionHelp.java
index dd3efc4d..e05f0aee 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/download/ConnectionHelp.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/download/ConnectionHelp.java
@@ -63,38 +63,50 @@ class ConnectionHelp {
   static HttpURLConnection setConnectParam(DownloadTaskEntity entity, HttpURLConnection conn)
       throws ProtocolException {
     conn.setRequestMethod(entity.requestEnum.name);
+    Set<String> keys = null;
     if (entity.headers != null && entity.headers.size() > 0) {
-      Set<String> keys = entity.headers.keySet();
+      keys = entity.headers.keySet();
       for (String key : keys) {
         conn.setRequestProperty(key, entity.headers.get(key));
       }
     }
-    conn.setRequestProperty("Charset", "UTF-8");
-    conn.setRequestProperty("User-Agent",
-        "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36");
-    StringBuilder accept = new StringBuilder();
-    accept.append("image/gif, ")
-        .append("image/jpeg, ")
-        .append("image/pjpeg, ")
-        .append("image/webp, ")
-        .append("image/*, ")
-        .append("application/xml")
-        .append("application/xaml+xml, ")
-        .append("application/xhtml+xml, ")
-        .append("application/x-shockwave-flash, ")
-        .append("application/x-ms-xbap, ")
-        .append("application/x-ms-application, ")
-        .append("application/msword, ")
-        .append("application/vnd.ms-excel, ")
-        .append("application/vnd.ms-xpsdocument, ")
-        .append("application/vnd.ms-powerpoint, ")
-        .append("text/plain, ")
-        .append("text/html, ")
-        .append("*/*");
-    conn.setRequestProperty("Accept", accept.toString());
-    conn.setRequestProperty("Accept-Encoding", "identity");
-    conn.setRequestProperty("Accept-Charset", "UTF-8");
-    conn.setRequestProperty("Connection", "Keep-Alive");
+    if (keys == null || !keys.contains("Charset")) {
+      conn.setRequestProperty("Charset", "UTF-8");
+    }
+    if (keys == null || !keys.contains("User-Agent")) {
+      conn.setRequestProperty("User-Agent",
+          "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36");
+    }
+    if (keys == null || !keys.contains("Accept")) {
+      StringBuilder accept = new StringBuilder();
+      accept.append("image/gif, ")
+          .append("image/jpeg, ")
+          .append("image/pjpeg, ")
+          .append("image/webp, ")
+          .append("application/xml, ")
+          .append("application/xaml+xml, ")
+          .append("application/xhtml+xml, ")
+          .append("application/x-shockwave-flash, ")
+          .append("application/x-ms-xbap, ")
+          .append("application/x-ms-application, ")
+          .append("application/msword, ")
+          .append("application/vnd.ms-excel, ")
+          .append("application/vnd.ms-xpsdocument, ")
+          .append("application/vnd.ms-powerpoint, ")
+          .append("text/plain, ")
+          .append("text/html, ")
+          .append("*/*");
+      conn.setRequestProperty("Accept", accept.toString());
+    }
+    if (keys == null || !keys.contains("Accept-Encoding")) {
+      conn.setRequestProperty("Accept-Encoding", "identity");
+    }
+    if (keys == null || !keys.contains("Accept-Charset")) {
+      conn.setRequestProperty("Accept-Charset", "UTF-8");
+    }
+    if (keys == null || !keys.contains("Connection")) {
+      conn.setRequestProperty("Connection", "Keep-Alive");
+    }
     //302获取重定向地址
     conn.setInstanceFollowRedirects(false);
     return conn;
diff --git a/Aria/src/main/java/com/arialyy/aria/core/download/DownloadUtil.java b/Aria/src/main/java/com/arialyy/aria/core/download/DownloadUtil.java
index 943294c7..2f08ba86 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/download/DownloadUtil.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/download/DownloadUtil.java
@@ -81,7 +81,7 @@ class DownloadUtil implements IDownloadUtil, Runnable {
         + ".properties");
     try {
       if (!mConfigFile.exists()) { //记录文件被删除，则重新下载
-        handleNewTask();
+        isNewTask = true;
         CommonUtil.createFile(mConfigFile.getPath());
       } else {
         isNewTask = !mDownloadFile.exists();
@@ -295,10 +295,6 @@ class DownloadUtil implements IDownloadUtil, Runnable {
       return;
     }
     int fileLength = conn.getContentLength();
-    if (fileLength < SUB_LEN) {
-      THREAD_NUM = 1;
-      CONSTANCE.THREAD_NUM = THREAD_NUM;
-    }
     Properties pro = createConfigFile(fileLength);
     int blockSize = fileLength / THREAD_NUM;
     int[] recordL = new int[THREAD_NUM];
@@ -325,7 +321,7 @@ class DownloadUtil implements IDownloadUtil, Runnable {
         recordL[rl] = i;
         rl++;
       } else {
-        handleNewTask();
+        handleNewTask(fileLength);
       }
       if (isNewTask) {
         recordL[rl] = i;
@@ -380,7 +376,7 @@ class DownloadUtil implements IDownloadUtil, Runnable {
     //分配每条线程的下载区间
     pro = CommonUtil.loadConfig(mConfigFile);
     if (pro.isEmpty()) {
-      handleNewTask();
+      handleNewTask(fileLength);
     } else {
       Set<Object> keys = pro.keySet();
       int num = 0;
@@ -390,7 +386,7 @@ class DownloadUtil implements IDownloadUtil, Runnable {
         }
       }
       if (num == 0) {
-        handleNewTask();
+        handleNewTask(fileLength);
         return pro;
       }
       THREAD_NUM = num;
@@ -400,7 +396,7 @@ class DownloadUtil implements IDownloadUtil, Runnable {
           if (state != null && Integer.parseInt(state + "") == 1) {
             continue;
           }
-          handleNewTask();
+          handleNewTask(fileLength);
           return pro;
         }
       }
@@ -412,9 +408,10 @@ class DownloadUtil implements IDownloadUtil, Runnable {
   /**
    * 处理新任务
    */
-  private void handleNewTask() {
+  private void handleNewTask(long fileLength) {
     isNewTask = true;
-    THREAD_NUM = AriaManager.getInstance(mContext).getDownloadConfig().getThreadNum();
+    THREAD_NUM = fileLength < SUB_LEN ? 1
+        : AriaManager.getInstance(mContext).getDownloadConfig().getThreadNum();
   }
 
   /**
diff --git a/app/src/main/assets/aria_config.xml b/app/src/main/assets/aria_config.xml
index 022b9800..f9ed36f3 100644
--- a/app/src/main/assets/aria_config.xml
+++ b/app/src/main/assets/aria_config.xml
@@ -4,7 +4,7 @@
   <!--注意，修改该配置文件中的属性会覆盖代码中所设置的属性-->
   <download>
 
-    <!--设置下载线程，线程下载数改变后，新的下载任务才会生效-->
+    <!--设置下载线程，线程下载数改变后，新的下载任务才会生效，如果任务大小小于1m，该设置也不会生效-->
     <threadNum value="4"/>
 
     <!--是否打开下载广播，默认为false，不建议使用广播，你可以使用Download注解来实现事件回调-->
diff --git a/app/src/main/java/com/arialyy/simple/test/TestMutilTaskSysDownload.java b/app/src/main/java/com/arialyy/simple/test/TestMutilTaskSysDownload.java
index 383536be..71b235e5 100644
--- a/app/src/main/java/com/arialyy/simple/test/TestMutilTaskSysDownload.java
+++ b/app/src/main/java/com/arialyy/simple/test/TestMutilTaskSysDownload.java
@@ -56,14 +56,17 @@ public class TestMutilTaskSysDownload extends BaseActivity<TestActivityMultiBind
     int maxNum = Aria.get(this).getDownloadConfig().getMaxTaskNum();
     for (int i = 0; i < urlArray.length; i++) {
       if (i < maxNum) {
+
         Aria.download(this)
             .load(baseUrl + urlArray[i])
             .setDownloadPath(Environment.getExternalStorageDirectory() + "/test/" + i + ".jpg")
+            //.addHeader("Accept-Encoding", "gzip,deflate,sdcn")
             .start();
       } else {
         Aria.download(this)
             .load(baseUrl + urlArray[i])
             .setDownloadPath(Environment.getExternalStorageDirectory() + "/test/" + i + ".jpg")
+            //.addHeader("Accept-Encoding", "gzip,deflate,sdcn")
             .add();
       }
     }