The aim of this study is to explore the DNA damage response of HeLa irradiated by ,12,C,6+, beam and the mechanism of the p53 activation change in this response. In our present study, double strands break(DSB) of HeLa cells irradiated with ,12,C,6+, beam were detected through neutral single cell gel electrophoresis, and AO/EB staining was used to detect the apoptosis of irradiated HeLa in 24h irradiation. Moreover, HeLa was pre-treated with caffeine (ATM and ATR inhibiting) or wormannin with certain concentrations (20μmol/L, ATM and DNA-PK inhibiting) and irradiated with 1Gy of ,12,C,6+, beam, and the expression of p53 was detected with Western blot analysis. The results show that DSB of HeLa caused by ,12,C,6+, beam increases with absorbed doses and decreases with the time after irradiation. The apoptosis percentage of irradiated HeLa increases with absorbed doses. It has been found that the p53 expression increases after irradiation, but has not significant increment with caffeine or wortmannin pre-treatment in cells. It can be deduced that the p53 activation is ATM-dependent, but not ATR and DNA-PK-dependent in HeLa DNA damage response induced by ,12,C,6+, beam.