Objectives To study the clinical effects and therapeutic mechanisms of the application of Chinese traditional medicine,the Decoction of Jie Du Hua Yu Tang,in the treatment of psoriasis.Meth-ods The clinical effects were observed in50patients with psoriasis vulgaris,to whom the Decoction of Jie Du Hua Yu Tang was given.The mice were used as experimental models whose tail scale epidermis was nat-urally lacking granular layer,similar to psoriatic epidermis.The mice were fed with Jie Du Hua Yu Tang and the effects on the formation of granular layer in their tail scale epidermis were noticed.Results The clinical cure rate was42%and the total response rate was90%with the Jie Du Hua Yu Tang.There was a signifi-cantly strong promoting effect on the formation of granular layer in mouse tail scale epidermis with the use of Jie Du Hua Yu Tang,in comparison with the control group.Conclusions The Decoction of Jie Du Hua Yu Tang is effective for the treatment of psoriasis vulgaris.The decoction could promote the formation of granu-lar layer in mouse tail scale epidermis.The therapeutic mechanism of the decoction may be related to the inhibition of proliferation of epidermal cells.