〓To explore the regulation role of Xiaoyinjiedu drink on peripheral blood T-lymphocytes in blood-heat syndrome of Ps(Psoriasis) patients by observing peripheral blood T lymphocytes and the expression of co-stimulatory factor changes of normal and Psoriasis patients, who received Xiaoyinjiedu Drink.Methods:Treatment group was given 8 weeks of medication, using flow cytometry, while comparison was made to the control group in terms of Peripheral Blood T-lymphocytes and Co-stimulatory factor CD28, CD80, CD86.Results:The treatment groups lesion scores decreased after treatment; CD3+, CD4+and CD4+/CD8+ is reduced when compared with normal group before and after treatment; CD28 was higher than the normal group before treatment, but lower than normal group after treatment; CD86 was significantly higher than the normal group before and after treatment; There was no significant difference between the normal group and treatment before, but after treatment there was a downward trend in CD80. There was no significant difference in the peripheral T-lymphocytes CD3+, CD4+, CD8+, CD4+/CD8+ and Co-stimulatory factor CD28, CD80, CD86 before and after treatment in the treatment group.Conclusion:Xiaoyinjiedu Drink has positive clinical effect. Psoriasis patients peripheral blood T-lymphocytes and Co-stimulatory factor have abnormal expression. It is uncertain whether the improvement of clinical symptoms of patients and the expression of T-lymphocytes and Co-stimulatory factor are parallel related.