I come to China since 1995. Have worked in Shanghai 5 years.

Dear Charlotte, according to relevant regulations, there is age limit. The age limit for male employees is 18 - 60, and 18 - 55 for female employees. However, in real practice, there is some flexibility. If you can find an employer who is willing to employ you, it may be possible to apply for it and you can have a try.
If it doesn't work, you can try to apply for an M type of multiple entries. However, it's a little bit troublesome because you need to exit and re-enter many times.