Objective:To investigate the effect of titanium modified by anodic oxidized TiO2 nanotubes on the osteogenic differentiation of human periodontal ligament stem cells(hPDLSCs). Methods:TiO2 nanotubes group and control group(smooth titanium)were involved in this study. The cell proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay. The osteogenic differentiation was evaluated using alkaline phosphatase(ALP)activity assay. In addition,osteogenic marker genes expression including Col-I,OCN and Runx-2 was evaluated. Results:We prepared nominally TiO2 nanotubes with 100 nm diameter on Ti substrates by anodization. No significant difference was detected on the proliferative activity at day 1 and the ALP activity at day 4 between the TiO2 nanotubes group and control group(P > 0.05). However,cell proliferative activity of TiO2 nanotubes group was lower than that of the control group at day 4 and 7. ALP activity assay demonstrated that the TiO2 nanotubes group at day 7,14 and 21 had a high ALP activity. The gene expression of Col-1,OCN,and Runx-2 of TiO2 nanotubes group was up-regulated at 21-days. Conclusion:The proliferation activity of hPDLSCs on the TiO2 nanotubes was less than that of control group. ALP activity,gene expression TiO2 nanotubes group were higher than those of on control group,and it suggested that TiO2 nanotubes could promote osteogenic differentiation of hPDLSCs.