Cross-priming is an important mechanism to activate immune response, which includes two classical signal pathways. Co-stimulatory signals are essential in the effective activation and B7-family is considered to be one of the most important factor in immunotherapy. PD-L1 is a new member of B7 family, whose ligand is PD-1. PD-1/PD-L1 can down-regulate the activation of immune response, which has become a focus of research. This article reviewed the expression of PD-1/PD-L1 in normal tissue and tumor, focusing on the status of PD-1/PD-L1 pathway study in leukemia, lymphoma, multiple myeloma, aplastic anemia and so on, in order to provide a new way for treatment of hematologic diseases.