Objective To observe the effect of Huoxue Jiedu Recipe（Herbal recipe for activating blood and removing toxins）on proliferation and cell cycle status of keratinocytes cultured in vitro in psoriasis.Methods Using the serum pharmacologic technique

the clean SD rats were adopted to make the Huoxue Jiedu Recipe medicated serum（high

moderate

low dose）

Dexamethasone medicated serum

and blank serum

which were added into the keratinocytes culture system respectively.After incubated for 48 hours

the cell proliferation of keratinocytes was measured by MTT assay

and the cell cycle distribution estimated with flow cytometer（FCM）.Results The different density of Huoxue Jiedu Recipe could all inhibit significantly the generation of COLO-16 keratinocyte line and change the distribution proportion of each phase in the cell division cycle.Conclusion Huoxue Jiedu Recipe treats psoriasis through inhibiting the proliferation of keratinocytes.