Abstract: Hepatic drug metabolism is a vital part of pharmacokinetics. Cytochrome P450 oxidase (CYP450) is the major drug metabolic enzyme in liver that is involved in the metabolism of 70%~80% of commonly used drugs in the clinic. Individual differences in the content and activity of CYP450 enzyme are the main causes of individual differences in drug effects. Based on the author's recent research results and literature reports, the effects of physiological content, activity and individual differences of human liver CYP450 enzyme, phenotype changes of CYP450 system, enzyme content and gene polymorphism on drug metabolism were reviewed, so as to provide reference for related clinical study.