Abstract: Objective To investigate the effects of total glucosides of paeony (TGP) on the proliferation and activation-induced cell death of mouse T cells and the mechanism underlying the immunosuppressive effects of TGP. Methods Purified total T cells isolated from the spleen of C57BL/6 mice were treated with TGP at 0, 50, 100, or 200 µg/mL and stimulated by anti-CD3/ CD28. Flow cytometry was performed to detect the cell death and the proliferation of CFSE-labeled T cells. The expression of Fas/FasL mRNA was detected using RT-PCR, and flow cytometry was used to analyze the expression of Fas/FasL proteins on activated T cells. Western blotting was used to detect the expression of Bcl-2 in the cells. Results TGP treatment for 48 h significantly reduced the total number and percentage of viable T cells and dose-dependently lowered the percentage of divided T cells. TGP treatment obviously up-regulated the cellular expression of Fas mRNA, enhanced Fas expression on the surface of the T cells, and decreased the expression level of Bcl-2 protein in the cells. Conclusion TGP significantly inhibits proliferation and promotes activation-induced cell death of mouse T cell by increasing the expression of Fas and downregulating the expression of Bcl-2.