@jiawen , having read through your post and the Q & A from my colleague @DaveF1006 , and being familiar with US-China Tax Treaty, would like to refer you to articles 4, 13 1nd 14 of the ref'd treaty.
Specifically, China taxes residents ( and not like US -- citizens ). Article 13 and 14 also refers to "employment executed " implying it allows taxation ONLY by the contracting state where residence is ( as long as it is more that 122 days. Thus my conclusion is that per the treaty China should not be taxing your wife's wages earned from work performed in the USA. Also IRS follows the same principle that the source of the income is where the work is performed.
Suggest you contact the employer to not tax her income for the work done while situated in the USA.
Please read through the treaty and the articles ref'd herein. It is available at www.irs.gov and search for "tax treaty".
Is there more I can do for you ?
