How long is the EASA ATPL theory exam valid?
FCL.025 is very clear on that and it says:


  (2) The completion of the airline transport pilot licence (ATPL) theoretical knowledge examinations will remain valid for the issue of an ATPL for a period of 7 years from the last validity date of:
  (i) an IR entered in the licence; or
  (ii) in the case of helicopters, a helicopter’s type rating entered in that licence.


ATPL theory exams are valid for 7 years of the date of expiry of IR, entered in EASA licence. So it depends when your EASA IR expired. ICAO IR unfortunately does not count in this case.

If your ATPL theory exams are not valid anymore, you will have to do them again. It is possible to transfer A320 rating from CAAC (ICAO) licence to an EASA one - depending on your experience. You would need, however, to do LST (licence skill test) on A320 in the simulator and pass all 14 EASA ATPL exams again.