Tumor immunotherapy, as one of the most promising research directions in the present field of oncotherapy, inhibits and kills tumor cells by enhancing anti-tumor immunity of the body. PD-1/PD-L1 inhibitors block negative control signals by inhibiting binding of PD-1 to its ligand PD-L1, leading to recovery of T cell activity and enhancement of immune response. In recent years, PD-1/PD-L1 inhibitors have shown good therapeutic effects in multiple tumor immunotherapies, making patients obtain long-term tumor remission and with controlled toxic and side effects. This article mainly reviewed the action mechanism and current situation of PD-1/PD-L1 inhibitors as well as their application effects in the treatment of various tumors.