Abstract: Objective 　To understand the inhibition and IC₅₀ (50 % inhibiting concent ration) of the recombinant adenoviral p53 gene ( rAd-p53) for the colorectal cancer cells in vitro and to guide clinical practice. Methods 　We evaluate the efficiency ( IC ₅₀ ) of the rAd2p53 and six kind of anti-cancer drugs (5-fluorouracil, tegafur, mitomycinc, cisplatin, oxaliplatin, paclitaxel) for human colorectal cancer cell line-174 through the cell culture and MTT chemosensitivity assay to make sure the anti-cancer capability of rAd-p53. Expression of p53 protein in t ransfection cells of colorectal cancer line-174 with rAd-p53 was evaluated by immunohistochemical stain. Results 　The rAd-p53 has good anti-cancer efficacy for the colorectal cancer cell line-174 in vitro, its IC₅₀ is 5. 73 ×10 ¹¹VP (viral particles) and it is dose-dependent and timedependent . But it s anti-cancer efficacy can′t be compared with the classical chemical medicine mitomycinc, 5-fluorouracil and cisplatin et al when it used alone. The immunohistochemistry stain in blank control group is negative. However five different density of rAd-p53 are all appeared positive result in infected colorectal cancer cells with rAd-p53 and earliest positive result presented at 24 hours after infection. Conclusion 　The rAd-p53 has good anti-cancer efficacy for the colorectal cancer cell line-174 in vitro, it is dose and time-dependent manner. But its anti-cancer efficacy worse than those of the classical chemical medicine mitomycinc, 5-fluorouracil and cisplatin etc. when it was used alone.