In this paper investigating inhibitory effect and radiation sensitization of recombinant adenovirus encoding human p53 tumor suppressor gene (rAd-p53) on human lymphoma cell lines has been performed by MTT, Laser confocal scanning microscope (LCSM) and flow cytometry. The results show that the inhibitory effect of rAd-p53 on human lymphoma cell lines is not obvious enough even though it is both dose-dependent and time-dependent. It has been found that cell inhibition and apoptosis ratios increases and cell cycle and morphology features changes apparently in radiation therapy and combined therapy. But there is no obvious difference in them. The results indicate that the transfection ratio of rAd-p53 on human lymphoma cell lines needs much improvement in order to strengthen the sensitivity of cell to radiation.