Hello dongyang

If you're referring to the Interface Language in wpDataTables' settings:

Please note that this language applies only to the interface.

The plugin actually has its own /languages/ folder and it can be translated using POEDIT or Loco Translate easily. I suggest installing Loco Translate since it's within WordPress and it has a simple UI.

If you want to use POEDIT then please follow these instructions:

1. Download wpdatatables from our TMS Store and save the wpdatatables.zip file on your computer.

2. Unzip downloaded file.

3. Download and install POEDIT. 

4. After that, open the program and open the file from the extracted folder on your computer wpdatatables/languages/en_US/wpdatatables.po.

5. Translate all the strings in your language.

6. Save the file as the plugin suggests (the language code; for example wpdatatables-id_ID.po if your language is Indonesian) and it will generate a new wpdatatables-id_ID.mo file. You can find your language code here. 

7. Go to wpdatatables/languages/ folder and create a new folder. Name it as the language code for your language (in our case, for Indonesian, it is id_ID) and then copy these two files called wpdatatables-id_ID.po and wpdatatables-id_ID.mo into it. Proceed with copying the whole folder id_ID back to your website in folder ../wp-content/plugins/wpdatatables/languages/.

Of course, you will use language code for your language (we use Indonesian language, and its language code "id_ID" is just an example).

When you finish that, it would be nice to send us the translation, so we can include it in our next major update so you don't have to copy this folder from the local machine on every update.

Hope this helps.