Objective: To evaluate the inhibitory effects of PIN1 antisense gene on the proliferation of human osteosarcoma cells. Methods: Different doses of antisense PIN1 gene (0,20,50,100,200,250μl) were transfected into osteosarcoma MG-63 cells. The cells and the culture supernatants before and after transfection were collected. The cell growth curve was made using MTT method. The cell growth cycle and apoptosis were detected by FCM. The expression of PIN1 was detected by Western blot. The expression of PIN1 mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR). Results: MTT and FCM assays indicated that the transfection of antisense PIN1 gene could inhibit proliferation of MG-63 cells and lead to cell apoptosis. Western-blot assays revealed the MG-63 cells transfected with antisense PIN1 gene had weaker expression than those without transfection with antisense PIN1 gene, and the band intensity was negatively related with doses. The cells transfected with different doses of gene (0,20,50,100,200,250 μl) had different absorbance rate(0.854 ± 0.136,0. 866 ± 0. 138,0. 732 ± 0. 154, 0. 611 ± 0. 121,0. 547 ± 0. 109,0. 398 ± 0. 113,0. 320 ± 0. 151 ), with significant difference assessed by F and q test ( P ＜ 0.05). The absorbance rate of PINI mRNA was 0. 983 ± 0.125,0.988 ± 0.127, 0.915 ± 0.157,0.786 ± 0.125,0.608 ± 0.124,0.433 ± 0.130,0.410 ± 0. 158 respectively ( P ＜ 0.05). Conclusion: The expression of PINlmRNA in MG-63 cells could be inhibited by antisense PIN1 gene, and then the expression of PIN1 was reduced and depressed, and so the proliferation of human osteosarcoma cells MG-63 was inhibited.