Objective: To compare the effect of Keyin Decoction(克银方)with retinoic acid in treatingpsoriasis. Methods: One hundred and six patients were randomly divided by paired grouping into the KYD group and the all-trans retinoic acid (RA) group, 53 in each group with 19 cases belonging to Wind-Heat Syndrome type and 34 to Wind-Dryness type. The Wind-Heat Syndrome type in the KYD group was trea- ted with KYD Ⅰ (with the action of rearing Heat, removing Dampness, cooling blood and dispelling Wind), and the Wind-Dryness type with KYD Ⅱ (with the action of nourishing blood, moistening skin and dredging Qi-blood circulation, ). The RA group was treated with RA. Sequential analysis was adopted to observe the effect. At the same time, the adverse reaction was observed. Results: When the test got to the 44th pair of patients, the scription of result reached the UA line of sequential chart, suggesting that the efficacy of KYD was superior to that of RA. Skin lesion subsidence rate in the KYD group and the RA group was 39.6% and 20.8% respectively with significant difference (P＜0.05). And for the patients of progressive phase in the two groups, skin lesion subsidence rate was 57.8% and 21.1% respectively (P＜0.05). No obvious adverse reaction was found in the KYD group. Conclusion: Keyin Decoction had goodeffect in treating psoriasis.