Abstract: ObjectiveTo explore the inhibitory effect of arsenic trioxide(ATO, As2O3) on the tumor growth of cervical cancer cell line HeLa subcutaneously implanted in nude mice and its mechanism. Methods Human cervical cancer xenografted model was established in nude mice.The tumor-bearing nude mice were randomly divided into the experimental groups： ATO low dose group ［2mg/（kg·d)］,ATO high dose group ［5mg/（kg·d)］,DDP positive control group ［3mg/（kg·d)］,saline negative control group(0.9%NaCl 0.2ml/d).The drugs were administered intraperitoneally for 10 consecutive days.To observe the tumor inhibition rate and effects of drugs.Ultramicrostructure feature of tumor was observed under electron microscope.Immunohistochemistry was used to measure the expression of p-P38 and Caspase-3. Results Inhibited tumor volume of ATO low and high dose groups and DDP positive control group was 22.95%,54.86% and 54.48%,respectively.The inhibited effect of ATO 5mg/kg/d group was similar with DDP 3mg/kg/d group, but the toxic effect of DDP was higher than ATO.The expression of p-P38 and Caspase-3 was higher than negative control group (P<0.05). Conclusion ATO can inhibit the growth of cervical cancer cells in vivo through enhancing apoptosis of tumor cells.