Peptidyl-prolyl cis-trans isomerase 1 （Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1，Pin1） is a small protein that regulates the level of phosphorylation in cells. Pin1 can specifically bind to the phosphorylated Serine/Threonine-Proline （pS/T-P） motif of phosphorylated target protein，and change the configuration of the target protein that it binds （from cis to Trans or change from trans to cis，Cis Trans）. This in turn leads to changes in the structural stability of the allosteric target protein or changes in its intracellular distribution and causes changes in cell functions，especially abnormal changes in the cell cycle，changes in growth and proliferation，and so on. Pin1 is overexpressed in most human malignant tumors，such as liver cancer，breast cancer，nasopharyngeal carcinoma，etc. It promotes the growth of tumor cells by breaking the balance between oncogenes and tumor suppressor genes. So some people call it a catalyst for tumorigenesis. This article reviews the research progress of Pin1's physiological properties and its role in various malignant tumors and provides theoretical references for tumor molecular targeted therapy.