Abstract： Objective To study the effect of the 18kDa translocator protein (TSPO) on U251cells of human glioma. Methods U251 cell line was cultured in vitro conventionally.The specific ligand ofTSPO,pk11195,was used in 5 experimental groups respectively with concentrations of 100,50,25,12.5 and 6.25 μmol/L,in comparison with a control group.MTr colorimetry and trypan blue staining were used to detect cell proliferation.Hoechst33342 staining and flow cytometry were applied to detect cell apoptosis. Western blotting and immumofluorescence method were used to detect the expression level of TSPO. DCFH-DA probe and GSH kit were used to respectively detect the level of reactive oxygen species (ROS) and GSH level in cells.Jc-1 staining was applied to detect the mitochondrial membrane potential.Luciferase enzyme was used to detect the quantity of ATP in cells. Results MTT showed the survival of U251 cells was significantly higher in the groups of 50 and 25 μmol/L pk11195than in the control group (P＜0.05). Trypan blue staining showed the cell death rate was significantlylower in the group of 50 μmol/L pk11195 than in the control group (P＜0.05).The apoptosis rate,TSPO expression,ROS and GSH levels decreased significantly in the groups of 6.25 and 50 μmol/L pk11195,compared with the control group; the apoptosis rate was significantly lower in the group of 50 μmol/Lpk11195 than in the group of 6.25 μmol/L pk11195 (P＜0.05).The cell membrane potential and ATP quantity were significantly higher in the groups of 6.25 and 50 μmol/L pk11195 than in the control group,and those in the group of 50 μmol/L pk11195 were significantly higher than in the group of 6.25 μmol/Lpk11195 (P＜0.05). Conclusion TSPO may promote apoptosis of U251 cells in human glioma and inhibit proliferation of glioma cells,functioning similarly as a cancer suppressor gene.