To observe therapeutic effects of Chaihu Shugan powder on premenstrual syndrome.Methods:Seventy patients were randomly divided to treatment group(n=35) and control group(n=35), respectively treated with modified Chaihu Shugan powder, or doxepin, oryzanol. The clinical effect and side effect were assessed with HAMA,SAS,SDS and TESS, as well as laboratory examination.Results:The effective rate of research group and control group were respectively 88% and 60% (P<0.01). After 4 and 8 weeks of treatment, HAMA scores of both groups significantly dropped with significant differences between them (P<0.05, P<0.01). After treatment SAS and SDS scores of both groups were significantly decreased when compared with the scores before treatment (P<0.01). The difference was significant between the two groups (P<0.01). Conclusion:Modified Chaihu Shugan powder has better effects on premenstrual syndrome than doxepin.