The invention discloses a [18F]AlF-labeled PET polypeptide probe and a preparation method thereof, comprising TMTP1 polypeptide and NOTA linked together, and its structural formula is as follows:. In the present invention, G-TMTP1 polypeptide is designed by adding a glycine to TMTP1 so that it does not affect its biological activity after being radiolabeled, and uses 18F as the radionuclide, and uses [18F]AlF-NOTA to mark G-TMTP1 Polypeptide, the obtained [18F]AlF-labeled PET polypeptide probe has excellent pharmacokinetic properties, fast background clearance rate, low liver uptake, good stability in vivo, high uptake in tumor sites, and high specificity for diagnosis Metastatic tumors can be used for the diagnosis or curative effect evaluation of highly metastatic malignant tumors.