Abstract: Fibroblast activation protein (FAP), as one of the molecular markers of cancer-associated fibroblasts (CAFs), is highly specifically expressed in activated CAFs. FAP can be used as a theranostic target for malignant tumors since it can promote tumor invasion, metastasis and immune escape. Gallium-68-labeled FAP inhibitor (⁶⁸Ga-FAPI) is a small molecular probe synthesized based on FAP, which can be visualized in vivo by PET/CT imaging. At present, ⁶⁸Ga-FAPI PET/CT has been successfully used in the diagnosis and staging of glioma, esophageal cancer, hepatocellular carcinoma, pancreatic ductal adenocarcinoma and other malignant tumors. This paper reviews the clinical application of ⁶⁸Ga-FAPI PET/CT in malignant tumors.