Objective:To evaluate the clinical efficacy of “Qinghua Tanshi Decoction” in the treatment of acne mastitis with phlegm-dampness syndrome. MethodsOne hundred and four subjects were randomized into the observation group and control group(52 cases in each group), and treated with topical herbal ointment; besides, the observation group was orally given “Qinghua Tanshi Decoction” and control group was given cefaclor capsules, with a course of two weeks. The clinical efficacy and symptoms scores were assessed.  Results:①The total effective rate was 94.2% in the observation group and 13.5% in the control group, with better efficacy in the observation group than in the control group(P<0.01); ②After treatment, the symptoms scores and total score reduced obviously(P<0.05, P<0.01), with lower symptoms scores and total score in the observation group than in the control group(P<0.05).  Conclusion:“Qinghua Tanshi Decoction” was quite effective on the acne mastitis with phlegm-dampness syndrome.