Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secretory serine protease, which is mainly expressed in hepatocytes. PCSK9 binds to low density lipoprotein receptor (LDLR) forming PCSK9-LDLR complex, and leads to LDLR degradation in lysosomes, which finally results in the reduction of cell membrane LDLR protein level and the elevation of plasma low density lipoprotein cholesterol (LDLC) level. PCSK9 inhibitors have become a hot spot in the research of hypercholesteremia and atherosclerotic cardiovascular disease (ASCVD) drugs discovery. There are three globally marketed PCSK9 inhibitors including evolocumab, alirocumab and PCSK9 siRNA drug inclisirian (Leqvio). This article reviewed the structure, functions and inhibitors of PCSK9.