Abstract: Provided are a binding protein targeting HER2, a preparation method and use thereof. The binding protein includes the following amino acid sequence (a): NDEMRX1TYW X2IALF X3 X4ML X5N X6X7KR X8 X9IR X10LYDDP X11X12A X13 X14LEX15 X16A X17LEA X18 X19 X20. The binding protein can bind to HER2 and has an excellent affinity with HER2. A radionuclide molecular imaging probe may be prepared by means of nuclide labeling, and it can be used in the molecular imaging diagnosis and improve the tumor imaging diagnosis to a molecular level of specific expression of tumor cells, and the HER2 expression in possible tumor lesions in vivo can be monitored in real time before a treatment scheme is determined or in the process of monitoring a medicament treatment progress.