Abstract: Fibroblast activation protein (FAP) is up-regulated in most solid tumors, making it a hot target for cancer diagnosis and therapy. Among FAP-targeting drugs, fibroblast activation protein inhibitor (FAPI) have gained significant attention by virtue of their high affinity and specificity, and are suitable to be used as ligands for radionuclide-targeted therapies due to their high aggregation in tumors and rapid clearance in normal tissues. In recent years, a large number of studies using FAPI as ligands for radionuclide therapy have been reported in the literature, and the relevant preclinical studies have prolonged the tumor retention time and improved the pharmacokinetics by drug design, while the relevant clinical studies have preliminarily demonstrated the effectiveness and safety of FAPI-associated radionuclide therapy. The authors reviewed current research on FAPI in tumor radionuclide therapy, aiming to provid references for subsequent related studies.