Abstract: Tumor immunotherapy is a breakthrough in the treatment of cancer in recent years. It has shown remarkable anti-tumor effects on a variety of malignant tumors. However, clinical application has revealed significant individual differences in the response of different patients, so individualized treatment has become a research hotspot. Positron Emission Tomography (PET) imaging is expected to play an important role in personalized medicine for cancer immunotherapy due to its high spatial resolution and sensitivity, no impact from endogenous substances as well as accurate positioning and quantification. PET imaging may aid in patient screening, dose optimization, drug efficacy prediction and evaluation, and safety assessment of tumor immunotherapy under living and non-invasive conditions. This article reviews the recent research advances of PET imaging in the individualized application of tumor immunotherapy, in the hope of providing reference for the development of clinical precision medicines for tumor immunotherapy.