Objective:To observe the therapeutic effect of Leyin (乐银, LY) in treating psoriasis mac-ulata (PM) and its effects on cellular immunity and vaginal epithelial cell mitosis in experimental mice.Methods: In this clinical study, 260 out-patients of PM were randomly divided into the observed group (n= 160) and the control group (n= 100), who were treated with oral intake of LY and Yinxieling granuleup study was also conducted on them. In the experimental study, delayed allergic model mice were treatedwith immunosuppressor (cyclophosphamide) and LY separately to observe the effects on their immunefunction and inhibition of vaginal epithelial cell proliferation. Results: In the observed group, 8 patients(5%) were cured, 32 (20%) basically cured, 48 (30%) markedly improved, 48 (30%) improved and 24(15 %) unchanged, the total effective rate being 85 %, while in the control group, the corresponding num-bers were 4, 8, 14, 38, 36 and 64% respectively, with the comparison of the total effective rate betweenthe two groups showing significant difference(P＜0. 01). Adverse reactions were not found in the study.Experimental study showed that LY could enhance the immune function of mice and had a certain inhibito-ry effect on vaginal epithelial cell proliferation. Conclusion: LY could treat PM effectively and shows im-mune enhancing and anti-mitosis effect in mice.