Abstract: Familial hypercholesterolemia (FH) is a common autosomal dominant dyslipidemia, which caused by mutations of the low-density lipoprotein receptor (LDLR) gene producing defect or deficiency in LDLR. The characters of FH are elevated level of total and LDL cholesterol. FH is considered to be a complex polygenic disease. Recently, more findings indicate that proprotein convertase subtilisin/kexin type 9 (PCSK9) gene play an important role in serum cholesterol metabolism. Some mutated PCSK9 proteins decrease LDLR, which cause FH in affected families. Some other mutated PCSK9 proteins decrease self-affinity, which cause hypocholesterolemia. We review the newest researches about the structure, function of PCSK9 gene and the relation of its mutations with plasma cholesterol metabolism.