Objective: To investigate the effects of miR-150 on expression of PD-1 in peripheral T cells and lung tumor growth in mice. Methods: miR-150 gene knockout (miR-150KO) and wild-type normal control (WT) mice were selected, number changes of peripheral T cells,expression of activated phenotype molecule CD69, and immune checkpoint molecule PD-1 were detected by flow cytometry. Lewis lung cancer cell line (LLC) was used to prepare transplanted tumor models in miR-150KO and WT mice by subcutaneous injection, and effect of miR-150 on growth of lung tumor was observed. Anti-PD-1 antibody was used to intraperitoneally inject miR-150KO and WT tumor-bearing mice, and its effect on tumor growth inhibition was observed. Results: Compared with WT mice, proportion and number of CD4+T cells in lymph nodes and spleen of miR-150KO mice were significantly increased, while proportion and number of CD4+T and CD8+T cells in peripheral blood were significantly decreased. miR-150 knockout resulted in a significant increase in proportion of CD69+ cells in CD4 T and CD8 T cells of lymph nodes and peripheral blood, as well as a significant increase in proportion of PD-1+ cells in CD4 T and CD8 T cells of peripheral blood. Compared with WT tumor-bearing mice, tumor growth was significantly accelerated in miR-150KO tumor-bearing mice, and proportion of PD-1+ cells in CD4 T and CD8 T cells in peripheral blood and lymph nodes of miR-150KO tumor-bearing mice was also significantly increased. Anti-PD-1 antibody treatment significantly inhibited tumor growth of miR-150KO tumor-bearing mice. Conclusion: miR-150 knockout promotes the growth of transplanted lung tumor in mice by increasing expression of PD-1 in T cells, but also enhances the immunosuppressive effect of anti-PD-1 antibody on tumor. [ABSTRACT FROM AUTHOR]