The work is to investigate effect of AdCMV-p53 gene transfer on the radiosensitivity of tumor cells. HepG2 (,wt,p53), Hela (,wt,p53, low level ,wt,p53 expression) and HT-29 (,mt,p53,mt,p53 over-expression) cells exposed to 0, 0.25, 0.5, 1.0, 1.5 and 2.0Gy were infected with AdCMV-GFP, a replication deficient recombinant adenoviral vector containing a CMV promoter and green fluorescent protein, or AdCMV-p53, a replication deficient recombinant adenoviral vector containing a CMV promoter and carrying human wild-type p53 gene. Survival fraction of the cells was determined by clonogenic assay. Survival curves were generated by linear quadratic model. The results showed that AdCMV-p53 infection could significantly promote the radiosensitivity of tumor cells. There is a relationship between the effect of AdCMV-p53 infection and the cellular intrinsic p53 status.