Objective: To study whether miR-21 targets and inhibits tumor suppressor gene PTEN can promote prostate cancer cell proliferation and invasion,Methods: Prostate cancer cell lines PC-3 were cultured and divided into negative control group(NC group),miR-21 group,pc DNA3.1 group,miR-21+pc DNA3.1 group and miR-21+PTEN group that were transfected with different mi R and plasmid,respectively,After 12 h and 24 h of transfection,the cell viability and invasive cell number were determined; after 24 h of transfection,Bcl-2,Survivin,MMP2,MMP9,PTEN,PI3 K,and AKT expression in cells were determined,Results: After 12 h and 24 h of transfection,OD value and invasive cell number of miR-21 group were significantly higher than those of NC group; after 24 h of transfection,Bcl-2,Survivin,MMP2,MMP9,PI3 K and AKT expression levels were significantly higher than those of NC group while PTEN expression level was significantly lower than that of NC group; after 12 h and 24 h of transfection,OD value and invasive cell number of mi R-21+pcDNA3.1 group were significantly higher than those of pc DNA3.1 group,and the OD value and invasive cell number of mi R-21+PTEN group were significantly lower than those of mi R-21+pcDNA3.1 group; after 24 h of transfection,Bcl-2,Survivin,MMP2 and MMP9 content of mi R-21+pc DNA3.1 group were significantly higher than those of pcDNA3.1 group,and Bcl-2,Survivin,MMP2 and MMP9 content of miR-21+PTEN group were significantly lower than those of mi R-21+pcDNA3.1 group,Conclusions: miR-21 can target and inhibit tumor suppressor gene PTEN expression to promote prostate cancer cell proliferation and invasion.