OBJECTIVE： To study the inhibitory effect of tankyrase inhibitor XAV939 on human osteosarcoma SOSP-9607 cells and its mechanism. METHODS： The human osteosarcoma SOSP-9607 cells were selected as research objects. The proliferation of osteosarcoma cells was determined by CCK-8 method after treated with 0.5， 1， 5， 10 μmol/L XAV939 for 24， 48， 72 h， and the inhibitory rate was calculated. After treated with 5 μmol/L XAV939 for 72 h， flow cytometry was applied to detect cell apoptosis and cell cycle distribution of osteosarcoma cells. Using glyceraldehyde-3-dehydrogenase （GAPDH） as internal reference， Western blot assay was used to detect the relative expression of β-catenin， Cyclin D1 and MMP-7 in osteosarcoma cells after treated with 0.5， 1， 5， 10 μmol/L XAV939 for 72 h. RESULTS： After treated with 1 μmol/L XAV939 for 72 h， 5， 10 μmol/L XAV939 for 24， 48， 72 h， the inhibitory rates of SOSP-9607 cells were increased significantly （P＜0.05 or P＜0.01）. After treated with 5 μmol/L XAV939 for 72 h， the apoptotic rate of SOSP-9607 cells was increased from 3.71％ to 21.03％ （P＜0.05）； the proportion of G1-phase cells increased from 45.5％ to 54.8％， that of S-phase cells decreased from 27.4％ to 24.0％， that of G2/M-phase cells decreased from 22.2％ to 16.2％ （P＜0.05）. After treated with 5， 10 μmol/L XAV939 for 72 h， the relative expression of β-catenin， Cyclin D1 and MMP-7 in SOSP-9607 cells decreased significantly（P＜0.05 or P＜0.01）. CONCLUSIONS： Tankyrase inhibitor XAV939 can inhibit the proliferation of human osteosarcoma SOSP-9607 cells， the mechanism of which may be associated with arresting cells at G1 phase and blocking signaling pathway of Wnt/β-catenin.