Objective:To investigate the effects of Tetramethylpyrazine(TMP)on telomerase activity and apoptosis in K562 cells lines and study the melocular mechanism of it's antileukemic.Methods:Cell apoptosis was observed by light microscopy and transmission electron microscopy.The expression of Fas was measured by flow cytometry.Polymerase chain reaction enzyme linked immunoassay(PCR-ELISA)was used to assay telomerase activity of K562 cells.Results:Tetramethylpyrazine could inhibit telomerase activity of K562 cells in a time-and-concentration-dependentmanner.Meanwhile,it could induce apoptosis obviously and up-regulate the levels of Fas in K562 cells.Conclusions:Tetramethylpyrazine could inhibit telomerase activity of K562 cells,and the mechanism of effect was maybe relate to inducing apoptosis and the expression of Fas protein.