Abstract: Objective To test whether umbilical cord mesenchymal stem cells (UMSCs) can inhibit the growth and metastasis of prostate cancer cells, and to investigate the mechanism. Methods The UMSCs from human umbilical cord tissue were isolate by explant technique. After being co-cultured the UMSCs with LNCaP and PC-3 cells for 24 h, 48 h and 72 h, LNCaP and PC-3 cells’ proliferation were tested and the 72 h proliferation inhibitory rate (IR) was calculated. Transwell invasion assay was used to test the migration and invasion abilities of prostate cancer cells after being co-cultured with UMSCs for 48 h. The invasion IR were calculated. The expression of matrix metalloproteinases (MMP)-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in the 72 h co-culture supernatants were tested by MILLIPLEX^?_MAPmethod. Results The proliferation of prostate cancer cells was inhibited after being co-cultured with UMSCs. The proliferation rate of LNCaP was lower than control group at 72 h (P<0.05), and the proliferation IR was 37.21%. The proliferation rate of PC-3 was lower than control group at 48 h and 72 h (P<0.05), and the proliferation IR was 31.27% at 72 h. Transwell invasion assays showed that co-culturing 48 h with UMSCs inhibited the invasive abilities of LNCaP and PC-3, and the invasion IR were 48.35% (LNCaP) and 46.91% (PC-3). Co-culturing 72 h, the expression of MMP-2 and MMP-9 were down-regulated (P<0.05) and the secretion of TIMP-1 and TIMP-2 were up-regulated (P<0.05) compared with control group. Conclusion UMSCs can inhibit the proliferation and invasion abilities of prostate cancer cells by secreting TIMPs, the antagonist of MMPs, which suppressed the overexpression of MMPs.