Objective:To observe the effects of Xiaoyin Decoction on immune function in patients of psoriasis vulgaris with syndrome of blood-heat. Methods78 patients of psoriasis vulgaris with syndrome of blood-heat were randomly divided into the control group and observation group,39 cases in each group. The control group was treated with routine therapy of western medicine,and the observation group was additionally treated with Xiaoyin Decoction based on the treatment for the control group,with a course of 2 months. The clinical efficacy of both groups was observed,and the changes of T lymphocyte subsets in peripheral blood and immune indexes of erythrocytes were compared before and after treatment.  Results:①The total effective rate was 82.05% in the control group and 97.44% in the observation group. The clinical efficacy of the observation group was obviously better than that of the control group(P,<,0.05). ②Compared with treatment before,the levels of CD3,+,CD4,+, and CD3,+,CD4,+, in peripheral blood were decreased(P,<,0.05)and the CD8,+, level was increased(P,<,0.05)in both groups. The improvement on all indicators in the observation group was better than that in the control group(P,<,0.05). ③After treatment,the FEIR level was decreased(P,<,0.05)and the levels of FEER,ATER and RBC-C3bR were increased(P,<,0.05)in both groups. The improvement on immune indexes of erythrocytes in the observation group was better than that in the control group(P,<,0.05).  Conclusion:Xiaoyin Decoction shows good clinical efficacy in the treatment of psoriasis vulgaris with syndrome of blood-heat,and can significantly improve the immune state of patients.