Abstract: Several programmed cell death protein 1 (PD-1) or its ligand (PD-L1) immune checkpoint blocking antibodies are available for clinical treatment, but only some patients show clinical response, so an alternative strategy for tumor immunotherapy is needed.A therapeutic tumor vaccine targeting PD-L1 is a meaningful attempt.In this study, we designed an epitope peptide vaccine targeting PD-L1, and then screened the immunogenic PD-L1 epitope peptide based on the humanized immune system (HIS) mouse model and further investigated its anti-tumor activity.The results show that the designed and screened PD-L1-B1 epitope peptide vaccine not only successfully induced PD-L1-specific humoral and cellular immunity, but also exhibit anti-tumor activity.In addition, immunotherapy increased T-lymphocyte infiltration of tumors and reshaped the tumor immunosuppressive microenvironment.In conclusion, PD-L1-B1 epitope peptide vaccine exhibits potent anti-tumor activity and may be an effective alternative immunotherapeutic strategy for patients insensitive to PD-1/PD-L1 blockade.