Abstract: Programmed cell death protein 1(PD-1)/programmed cell death ligand 1(PD-L1) is a pair of important immune checkpoint in tumor immunotherapy. PD-L1 expressed mainly in tumor cells and tumor-associated myeloid cells. The radionuclide-labeled molecular probe targeting PD-L1 can be detected by PET/CT and visualize PD-L1 expression at the molecular level, which is an important method to guide immunotherapy. PET probes targeting PD-L1 include antibodies, peptides, small molecules, and other probes, and some of them are currently used in clinical applications. This article reviews molecular probes targeting PD-L1 and their clinical applications.