CYP2D6,as a member of cytochrome P450 family,is an important drug-metabolizing enzyme which catalyzes metabolism of a wide variety of drugs.It has been shown for years that the gene coding CYP2D6 enzyme has genetic polymorphism,which shows a close relationship with drug metabolism,adverse drug reaction and activation of carcinogenic substance.With the completion of human genome project and the beginning of gene polymorphism research project,the researches about polymorphism of CYP2D6 gene,and its relationship with clinical phenotypes has become one of important topics in the area of pharmacokineties.We will review CYP2D6 gene polymorphism,its production,and its influences on drug metabolism and susceptibility to certain diseases.