回複：請教：如何辦理國內的工作證明？

You will just need to write a letter and ask your boss in China to sign it. In the letter, you should state where you worked, when you worked there, what job you worked, and what title you had. If you had some papers published or some achivements, you may write you wrote some papers and got some achievements when you worked there. Please remember. The job you had in China should match your current job.