Abstract: Programmed cell death 1 receptor (PD-1) and its ligand (PD-L1) immunotherapy has become an important method for the treatment of a variety of malignant tumors, but only some patients have clinical benefits. One of the influencing factors is the expression level of PD-1/PD-L1 in malignant tumors. Radionuclide labeled complete monoclonal antibodies and antibody fragments are used to make targeted PD-1/PD-L1 radionuclide molecular probes for imaging, which can noninvasively, real-time, and dynamically monitor the expression of tumor PD-1/PD-L1 and quantify its expression level, so as to screen patients suitable for treatment and comprehensively evaluate the treatment efficacy and prognosis. The authors review the application of targeted PD-1/PD-L1 radionuclide molecular probes in malignant tumors.