Objective To observe therapeutic effect and side effect of finasteride on acne patients.Method Fifty-six ance patients who are divided into male and female groups take 5mg finasteride for 2 months.Summarize therapeutic effect by evaluating accumulated points of patients,meanwhile evaluate side effect of finasteride.Result Acne erythra area and severity are lessened in both male and female groups after taking finasteride,and no apparent side effect is observed.Conclusion Therapeutical effect of finasteride on acne is satisfactory and side effect is seldom.