Objective To observe the effect of Yinxieling Prescription(YP)and its modified prescriptions on keratinocyte HaCaT proliferation,and to screen the effective components of YP.Methods Orthogonal design was adopted for the preparation of 12 modified prescriptions of YP.With lipopolysaccharide(LPS) as the stimulating factor,human in-vitro hyperproliferation keratinocyte HaCaT model was established.The effect of YP and its modified prescriptions at different concentrations on the proliferation of keratinocyte HaCaT was examined by methyl thiazolyl tetrazolium(MTT)assay.The correlation of effect with time was also investigated.Results YP had inhibitory effect on the proliferation of keratinocyte HaCaT,and the effect was correlated with the concentration and action time.Modified prescriptions 7 and 8 inhibited the proliferation of keratinocyte HaCaT obviously,and the difference was significant as compared with LPS model group(P0.05).Conclusion The therapeutic mechanism of YP for psoriasis may be related with the inhibition of keratinocyte HaCaT proliferation,and the components of modified prescriptions 7 and 8 probably are the effective components of YP.