Abstract: To study the effect of cimetidine on cytochrome P450, CYP2E1, blood sugar, insulin and othert indexes in nonalcoholic steatohepatitis (NASH) rats.30 male SD rats were randomly divided into three groups, control group (n=10) , model group (n=10) and therapeutic group (n=10) .The therapeutic group received cimetidine 200mg daily for 12 weeks.The rats were taken the blood by cutting tails at the 4th, 6th, 8th, 10th and 12th weeks during the study.In the first 4 times, the level of serum AST, ALT and blood sugar was measured.And at the last time, CYP450, CYP2E1, blood sugar, insulin, ALT, AST, TG, TC, LDL, and HDL were measured.We also observe the histologic characters of NASH rats.We observed the levels of ALT, AST, blood sugar in model group increased significantly, then kept increasing through the study.The decrease of CYP450, CYP2E1 in therapeutic groups was obvious.There was an obvious difference of ALT, AST between therapeutic group and model group, while the other indexes be not obviously distinguished from each other.The hepatic injury in therapeutic groups was significantly lessened.So cimetidine can prevent nonalcoholic hepatic injury, inhibit the expressions of CYP450 and CYP2E1, and decrease the expression of ALT and AST, but have no effect on blood sugar, insulin, TG, TC and lipoprotein.