Tsinghua, Peking University, Fudan University, Zhejiang University and Shanghai have strong traffic.

Others, Wuhan University, have been to the finals.

Hangzhou Dianzi University, OJ is very famous and should attach great importance to ACM.

Harbin Institute of Technology is also good.

And then ... I don't know = =

You might as well go to their OJ forum and ask.

acm.hdu.edu.cn

acm.hit.edu.cn

acm.pku.edu.cn

etc