Abstract: At present, one of the difficulties in the clinical diagnosis and treatment of tumors is to find specific targets and highly selective targeted inhibitors. Fibroblast activation protein (FAP) is a type Ⅱ transmembrane serine protease of the proline oligopeptidase family. A large number of studies have shown that FAP is overexpressed in cancer associated fibroblasts (CAFs) of various tumor entities, and plays important a role in the growth, invasion, metastasis, angiogenesis and immune escape of tumor cells. This suggesting that FAP may become a specific target for tumor diagnosis and treatment. In addition to being highly expressed in inflammation and fibrosis-related diseases, FAP is not normally expressed in normal tissues and organs of adults, so radionuclide-labeled FAP inhibitors have low background activity and can obtain high-contrast images. This article mainly describes the research progress of radionuclide-labeled small molecule FAP inhibitors in terms of affinity, selectivity, structure-activity relationship, in vivo metabolism, and clinical research of FAP inhibitors, in order to benefit clinical diagnosis and treatment.