diff --git a/Aria/src/main/java/com/arialyy/aria/core/download/DownloadTarget.java b/Aria/src/main/java/com/arialyy/aria/core/download/DownloadTarget.java
index b8afcd17..0d18ce41 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/download/DownloadTarget.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/download/DownloadTarget.java
@@ -74,6 +74,13 @@ public class DownloadTarget extends AbsTarget<DownloadEntity, DownloadTaskEntity
     return this;
   }
 
+  /**
+   * 下载任务是否存在
+   */
+  @Override public boolean taskExists(String downloadUrl) {
+    return DownloadTaskQueue.getInstance().getTask(downloadUrl) != null;
+  }
+
   /**
    * 设置请求类型
    *
diff --git a/Aria/src/main/java/com/arialyy/aria/core/inf/AbsTarget.java b/Aria/src/main/java/com/arialyy/aria/core/inf/AbsTarget.java
index ac2d4204..f73e8f85 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/inf/AbsTarget.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/inf/AbsTarget.java
@@ -23,6 +23,7 @@ import com.arialyy.aria.core.RequestEnum;
 import com.arialyy.aria.core.command.AbsCmd;
 import com.arialyy.aria.core.command.CmdFactory;
 import com.arialyy.aria.core.download.DownloadEntity;
+import com.arialyy.aria.core.queue.DownloadTaskQueue;
 import com.arialyy.aria.core.upload.UploadEntity;
 import com.arialyy.aria.orm.DbEntity;
 import com.arialyy.aria.util.CommonUtil;
@@ -74,6 +75,13 @@ public class AbsTarget<ENTITY extends IEntity, TASK_ENTITY extends ITaskEntity>
     return -1;
   }
 
+  /**
+   * 下载任务是否存在
+   */
+  public boolean taskExists(String downloadUrl) {
+    return false;
+  }
+
   /**
    * 获取当前任务进度，如果任务存在，则返回当前进度
    *
diff --git a/Aria/src/main/java/com/arialyy/aria/core/queue/DownloadTaskQueue.java b/Aria/src/main/java/com/arialyy/aria/core/queue/DownloadTaskQueue.java
index 7288fde6..a40d92b5 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/queue/DownloadTaskQueue.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/queue/DownloadTaskQueue.java
@@ -160,9 +160,13 @@ public class DownloadTaskQueue
   }
 
   @Override public DownloadTask getTask(DownloadEntity entity) {
-    DownloadTask task = mExecutePool.getTask(entity.getDownloadUrl());
+    return getTask(entity.getDownloadUrl());
+  }
+
+  @Override public DownloadTask getTask(String url) {
+    DownloadTask task = mExecutePool.getTask(url);
     if (task == null) {
-      task = mCachePool.getTask(entity.getDownloadUrl());
+      task = mCachePool.getTask(url);
     }
     return task;
   }
diff --git a/Aria/src/main/java/com/arialyy/aria/core/queue/ITaskQueue.java b/Aria/src/main/java/com/arialyy/aria/core/queue/ITaskQueue.java
index 0b9b18af..7f05cbff 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/queue/ITaskQueue.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/queue/ITaskQueue.java
@@ -89,6 +89,14 @@ public interface ITaskQueue<TASK extends ITask, TASK_ENTITY extends ITaskEntity,
    */
   public TASK getTask(ENTITY entity);
 
+  /**
+   * 通过工作实体缓存池或任务池搜索下载任务，如果缓存池或任务池都没有任务，则创建新任务
+   *
+   * @param url 链接地址，如果是下载，则为下载链接，如果是上传，为文件保存路径
+   * @return {@link DownloadTask}、{@link UploadTask}
+   */
+  public TASK getTask(String url);
+
   /**
    * 通过工作实体删除任务
    *
diff --git a/Aria/src/main/java/com/arialyy/aria/core/queue/UploadTaskQueue.java b/Aria/src/main/java/com/arialyy/aria/core/queue/UploadTaskQueue.java
index 9b7c061a..0dc69cee 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/queue/UploadTaskQueue.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/queue/UploadTaskQueue.java
@@ -96,9 +96,13 @@ public class UploadTaskQueue extends AbsTaskQueue<UploadTask, UploadTaskEntity,
   }
 
   @Override public UploadTask getTask(UploadEntity entity) {
-    UploadTask task = mExecutePool.getTask(entity.getFilePath());
+    return getTask(entity.getFilePath());
+  }
+
+  @Override public UploadTask getTask(String url) {
+    UploadTask task = mExecutePool.getTask(url);
     if (task == null) {
-      task = mCachePool.getTask(entity.getFilePath());
+      task = mCachePool.getTask(url);
     }
     return task;
   }
diff --git a/Aria/src/main/java/com/arialyy/aria/core/upload/UploadTarget.java b/Aria/src/main/java/com/arialyy/aria/core/upload/UploadTarget.java
index 1276d1d2..58296f38 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/upload/UploadTarget.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/upload/UploadTarget.java
@@ -100,6 +100,13 @@ public class UploadTarget extends AbsTarget<UploadEntity, UploadTaskEntity> {
     return this;
   }
 
+  /**
+   * 下载任务是否存在
+   */
+  @Override public boolean taskExists(String downloadUrl) {
+    return UploadTaskQueue.getInstance().getTask(downloadUrl) != null;
+  }
+
   /**
    * 设置请求类型
    *
diff --git a/Aria/src/main/java/com/arialyy/aria/orm/DbUtil.java b/Aria/src/main/java/com/arialyy/aria/orm/DbUtil.java
index 0e14dea1..79a94c20 100644
--- a/Aria/src/main/java/com/arialyy/aria/orm/DbUtil.java
+++ b/Aria/src/main/java/com/arialyy/aria/orm/DbUtil.java
@@ -21,13 +21,9 @@ import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.support.annotation.NonNull;
-import android.text.TextUtils;
 import android.util.Log;
 import com.arialyy.aria.util.CheckUtil;
 import com.arialyy.aria.util.CommonUtil;
-import java.lang.reflect.Field;
-import java.util.ArrayList;
-import java.util.Date;
 import java.util.List;
 
 /**
@@ -73,7 +69,7 @@ public class DbUtil {
    */
   synchronized <T extends DbEntity> void delData(Class<T> clazz, String... expression) {
     CheckUtil.checkSqlExpression(expression);
-    mDb = mHelper.getWritableDatabase();
+    checkDb();
     SqlHelper.delData(mDb, clazz, expression);
   }
 
@@ -81,7 +77,7 @@ public class DbUtil {
    * 修改某行数据
    */
   synchronized void modifyData(DbEntity dbEntity) {
-    mDb = mHelper.getWritableDatabase();
+    checkDb();
     SqlHelper.modifyData(mDb, dbEntity);
   }
 
@@ -89,9 +85,7 @@ public class DbUtil {
    * 遍历所有数据
    */
   synchronized <T extends DbEntity> List<T> findAllData(Class<T> clazz) {
-    if (mDb == null || !mDb.isOpen()) {
-      mDb = mHelper.getReadableDatabase();
-    }
+    checkDb();
     return SqlHelper.findAllData(mDb, clazz);
   }
 
@@ -99,7 +93,7 @@ public class DbUtil {
    * 条件查寻数据
    */
   synchronized <T extends DbEntity> List<T> findData(Class<T> clazz, String... expression) {
-    mDb = mHelper.getReadableDatabase();
+    checkDb();
     return SqlHelper.findData(mDb, clazz, expression);
   }
 
@@ -108,7 +102,7 @@ public class DbUtil {
    */
   @Deprecated synchronized <T extends DbEntity> List<T> findData(Class<T> clazz,
       @NonNull String[] wheres, @NonNull String[] values) {
-    mDb = mHelper.getReadableDatabase();
+    checkDb();
     return SqlHelper.findData(mDb, clazz, wheres, values);
   }
 
@@ -116,9 +110,7 @@ public class DbUtil {
    * 插入数据
    */
   synchronized void insertData(DbEntity dbEntity) {
-    if (mDb == null || !mDb.isOpen()) {
-      mDb = mHelper.getReadableDatabase();
-    }
+    checkDb();
     SqlHelper.insertData(mDb, dbEntity);
   }
 
@@ -126,17 +118,19 @@ public class DbUtil {
    * 查找某张表是否存在
    */
   synchronized boolean tableExists(Class clazz) {
-    if (mDb == null || !mDb.isOpen()) {
-      mDb = mHelper.getReadableDatabase();
-    }
+    checkDb();
     return SqlHelper.tableExists(mDb, clazz);
   }
 
   synchronized void createTable(Class clazz, String tableName) {
+    checkDb();
+    SqlHelper.createTable(mDb, clazz, tableName);
+  }
+
+  private void checkDb(){
     if (mDb == null || !mDb.isOpen()) {
-      mDb = mHelper.getWritableDatabase();
+      mDb = mHelper.getReadableDatabase();
     }
-    SqlHelper.createTable(mDb, clazz, tableName);
   }
 
   /**
@@ -159,7 +153,7 @@ public class DbUtil {
    * 获取所在行Id
    */
   synchronized int[] getRowId(Class clazz) {
-    mDb = mHelper.getReadableDatabase();
+    checkDb();
     Cursor cursor = mDb.rawQuery("SELECT rowid, * FROM " + CommonUtil.getClassName(clazz), null);
     int[] ids = new int[cursor.getCount()];
     int i = 0;
@@ -176,7 +170,7 @@ public class DbUtil {
    * 获取行Id
    */
   synchronized int getRowId(Class clazz, Object[] wheres, Object[] values) {
-    mDb = mHelper.getReadableDatabase();
+    checkDb();
     if (wheres.length <= 0 || values.length <= 0) {
       Log.e(TAG, "请输入删除条件");
       return -1;