Abstract: Human epidermal growth factor receptor 2 (HER2) is expressed in various tumors. Trastuzumab can significantly improve the overall survival time of HER2-positive breast cancer and gastric cancer patients. At present, the detection methods of HER2 overexpression are mainly IHC and FISH. However, this invasive examination can not be used as a routine examination. PET/CT molecular imaging targeting HER2 is expected to monitor the HER2 expression in whole-body lesions in real time and non-invasively. At present, PET/CT molecular imaging targeting HER2 mainly includes nuclide-labeled antibody imaging, nuclide-labeled affibody/antibody fragment/nanoantibody imaging. It can be used to monitor the expression and the heterogeneity of HER2, screen positive metastatic foci in patients with primary HER2-negative breast cancer and predict the curative effect. Long half-life nuclide (⁶⁴Cu, ⁸⁹Zr) labeled intact antibody can directly assess the situation of HER2 binding to trastuzumab, but its blood pharmacokinetics and blood clearance are slow, and long-time imaging is needed. In addition, the long half-life nuclides lead to higher radiation dose. Short half-life nuclide (⁶⁸Ga) labeled affibody /antibody fragment/nanoantibody imaging, due to its small molecular weight, fast biological distribution and short-time imaging (1-4h) after the injection of drugs, can increase the convenience of the patients and be repeatedly imaged. As the binding site is different from antibody, affibody can be used for the imaging in target therapy. Also, the radiation caused by short half-life nuclide is significantly lower than that by long half-life nuclides, and may be more suitable for clinical application.