Objective：To study the identification the stem property of CD133+ liver cancer cells and inhibition effect of 131I-labeled monoclonal antibody（mAb）against CD133 on them in vitro and vivo. Methods：The monoclonal antibody CD133 labeled with 131I was prepared using the chloramines-T method and its stability was evaluated. Magnetic-activated cell sorting（MACS） was used to isolate CD133 and CD133- cells from HepG2 cells. Flow cytometry（FCM） was used to detect the expression of CD133 before and after the cell isolation. The stem cell properties of sorted CD133 cells were validated by sphere-forming assay，colony formation assay in vitro and tumorigenesis experiment in vivo. There were four groups including 131I-labeled anti-CD133 mAb group，131I group，CD133 mAb group and 131I CD133 mAb group. The inhibitory effects of different treatments on the proliferation of CD133 cells were measured by MTT assy. The animal model was established by subcutaneous inoculation of CD133 -HepG2 cells（5×104） to right front legs of BALB/c mice. After tumor model being established，12 mice were randomly divided into 4 groups. Drugs were injected into the tail vein of the nude mice at a frequency of one time/2 d（14 times in total）. The tumor size and volume were measured twice a week after the treatment and the tumor inhibitory rate was calculated. After 4 weeks，the mice were sacrificed for pathological examination. Results：The labeling ratio of the 131I-labeled anti-CD133 mAb was 89.34% and the radiochemical purity was 98.21%. The sorted CD133 cells showed a high purity（98.46±0.97）% compared with that before cell sorting（1.78±0.54）%. CD133 cells showed a high tumor sphere formation ability and turmorigenesis capacity compared with those of CD133- cells. The tumor inhibitory rate of CD133 cells was significantly higher in 131I-labeled anti-CD133 mAb group than in 131I group，CD133 mAb group and blank control group in vivo and vitro（P<0.05）. Conclusion：１31I-labeled anti-CD133 mAb can effectively inhibit the growth of CD133 -HepG2 cells in vivo and vitro.