Abstract: Objective To investigate the effects of trichostatin A(TSA) on cytotoxicity and radiosensitivity of human cervical cancer cell line HeLa. Methods HeLa cells were treated with different concentrations of TSA for 12, 24, 48 and 72 hours.Cell proliferation and radiosensitizing effect of IC10 TSA combining different low dose of fractionated radiotherapy was detected by methylthiazolyl tetrazolium (MTT) assay.Cloniesformation was used to determine the radiosensitization effect induced by 10％ inhibition concentration of TSA. Results TSA siginificantly inhibited the proliferation of HeLa cells in a dose-and time-dependent manner，the 50％ inhibition concentration and 10％ inhibition concentration of co-treatment with TSA for 24 hours were 0.0312 and 0.5865 μmol/L,respectively;and when concentration over 0.6 μmol/L and treatment time longer than 48 hours,TSA showed no more cytotoxicity.When exposed to TSA for 24 h, the SER of HeLa cells was 1.6858,SERS of IC10 TSA combining 2.0 Gy/time,1.0 Gy/time（×2）,0.5 Gy/time （×4） fractionated radiotherapy groups were 1.4496,1.6410 and 1.9554,respectively. Conclusion TSA can significantly enhance radiosensitivity of HeLa cells,especially combining with low dose fractionated radiotherapy.