In this paper, the cytotoxicity of EGCG against PC-3 prostate cancer cells and its molecular mechanism in the presence and absence of Zn2+ in vitro were investigated. The results showed that both EGCG and Zn2+ suppressed clonegenecity of PC-3 cells, and the suppression effect was enhanced in the coexist system of EGCG and Zn2+. MMP-9 is thought to play a significant role in cancer cell migration and invasion. In the present paper, the results showed that EGCG suppressed the activity of MMP-9 in PC-3 cells in the presence of Zn2+, as a result, migration ability of the cells was significantly decreased.