Abstract: Objective:To investigate the impact of Arsenic Trioxide on telomerase activity and human telomerase reverse transcriptase （hTERT） in HeLa cell. Methods: The Hela cells were cultured and exposed to 2μmol/L As₂O₃ during different time, at the different time point, the cell's proliferation activity were measured by MTT, the distribution of cell cycle were determined by flow cytometry, the expression of hTERT mRNA were measured by RT-PCR, the activity of telomerase were measured by TRAP-ELISA. Results: The Hela cell's proliferation activity was gradually decreased after exposed to 2μmol/L As₂O₃, the number of cells in the G_O/G₁ phase increased and S phase decreased. The expression of hTERT mRNA was gradually weakened and the telomerase activity was decreased. Conclusions: As₂O₃ has cells cycles stopping effection on HeLa cell, and it can weaken the expression of human telomerase reverse transcriptase （hTERT） and decreased the telomerase activity.