Abstract: Objective To study the therapeutic effects of koumine on psoriasis in mouse models.Methods The effects of koumine on epithelial cell mitosis and epidermal cell differentiation was evaluated by collecting the samples of the vaginal mucous and squamous epidermis at the tail of mice treated with methotrexate or koumine at different doses. The levels of interleukin (IL)-2 were detected with enzyme-linked immunosorbent assay.Results High and intermediate doses of koumine showed remarkable inhibitory effect on mouse vaginal epithelial cell mitosis and promoted the formation of epidermal granular layer in the scales at the mouse tail. Three concentrations at 6, 30, 150 mg/kg of koumine decreased serum IL-2 level in the mice.Conclusion The therapeutic effect of koumine against psoriasis is related to the inhibition of epidermal cell proliferation, promoting the formation of granular cells and decreasing the serum level of IL-2.