Objective: To investigate the effect of ginsenoside Compound K (C-K) on the apoptosis, immunosuppression and pro-inflammatory cytokine secretion of myeloid derived suppressor cell (MDSC). Methods: Flow cytometry sorted CT26 tumor mouse bone marrow MDSCs. After treatment with CK or PBS, Annexin V/7-AAD was used to detect apoptosis; qRT-PCR was used to detect the mRNA expression levels of Cox-2 and Arg-1 ; ELISA technology to detect the levels of IL-1β, IL-6 and IL-17 in the cell culture supernatant. In in vivo experiments, Balb/c mice were subcutaneously immunized with C-K or control PBS-treated MDSCs and colon cancer cell line CT26. After 21 days, the tumor size and histomorphology of the two groups of mice were identified. Results: CK promoted the apoptosis of MDSC cultured in vitro, which showed that the rate of early cell apoptosis and late apoptotic cell or necrosis rate increased (P<0.01, P<0.05); and it significantly down-regulated the immunosuppressive effect of MDSC. The expression of genes Cox-2 and Arg-1 (P<0.05, P<0.01); simultaneously inhibited the secretion of pro-inflammatory cytokines IL-1β, IL-6 and IL-17 in MDSC (P<0.05, P<0.001) , P<0.05). Compared with the control group, the MDSCs treated with C-K significantly weakened the proliferation of tumor cells in vivo (P<0.01). Conclusion: C-K can promote the apoptosis of MDSC cells cultured in vitro and antagonize its immunosuppressive function, thereby inhibiting the growth and proliferation of tumor cells.