is it possible to change the S1 visa into X1 study type

Dear
Currently my wife has S1 type here in China. currently she decided to study PhD here.
Is it possible for her to change her S1 into X1 study type? At present she has temporary residence permit according to her S1type.
I am kind of confused in this situation. By the way her residence permit is going to expire within 1 month time.
Thanks
Regards,
Abdul (Pakistan)