Abstract: Objective 　To evaluate telomerase activity of human gastric cancer cell Line BGC-823 cultured with different concent ration of Arsenic Trioxide and genetic t ranscription level of human telomerase reverse transcriptase (hTERT) . Methods 　The cell activity of BGC-823 cells was measured using MTT method af ter BGC-823 cells cultured with various concent rations of As₂ O₃ . Changes in apoptosis of BGC-823 cells were analyzed with flow cytometry ( FCM) . Telomerase activity was determined by telomeric repeat amplification protocol PCR EL ISA ( TRAP PCR EL ISA) . The mRNA level of hTERT gene was tested by semi-quantitive RT-PCR. Results 　The proliferation of BGC-823 cells cultured with As₂ O₃was significantly inhibited and result in cells apoptosis. The tendency of proliferation inhibition depended on As₂ O₃ dose increasing and administ rated time prolong. Meanwhile, telomerase activities were markedly decreased and genetic t ranscription expressions of hTERT were obviously suppressed. These changes also show obvious time-Dose-response relationship . Conclusion 　As₂ O₃ could inhibit the generation of BGC-823 cells and activation of telomerase. It maybe a good telomerase inhibitor, this is value for clinical application of tumor therapy.