Abstract: Cyclin-dependent kinase (CDK) plays an important role in cell cycle regulation and gene transcription. CDK12 can participate in gene transcription regulation by regulating gene transcription extension, RNA splicing, transcription termination and DNA damage repair (DDR). It is found that the dysregulation of CDK12 is related to the tumorigenesis and tumor metastasis. This article introduces the structure and biological functions of CDK12 as well as its relationship with tumors, and reviews the research progress in CDK12 inhibitors, aiming to provide reference for further research on the mechanism of CDK12 and the development in CDK12 inhibitors.