To observe the effect of Compound Qingdai Capsule on skin lesions and Th1/Th2 shift related factors in serum of patients with advanced psoriasis vulgaris，and analyze the correlation between the factors and skin lesion index.Methods:A total of 80 patients with advanced psoriasis vulgaris treated in the First Affiliated Hospital of Heilongjiang University of Chinese Medicine from October 2019 to October 2020 were included and divided into an observation group(n=38) and a control group(n=42) by random number table.The observation group took Compound Qingdai Capsule while the control group took Compound Glycyrrhizin Tablets.The areas of erythema，infiltration，scale and skin lesions in the two groups were detected，and Psoriasis Area and Severity Index(PASI) was used to evaluate the overall clinical efficacy.The serum levels of Th1 cell secretory factors IL-2，IFN-γ，TNF-α and Th2 cell secretory factors IL-4 and IL-10 were measured by enzyme linked immunosorbent assay(ELISA).The correlation between △PASI and the changes of Th1/Th2 shift related factors was analyzed.Results:Compound Qingdai Capsule alleviated the erythema，infiltration and scale state of skin lesions in patients(P<0.01)，reduced the lesion area(P<0.01)，and improved the PASI and △PASI score(P<0.05).The Compound also down regulated the content of secretory factors of Th1 cells and up regulated that of Th2 cells(P<0.01).There was a positive correlation between △PASI and the changes of Th1/Th2 shift related factors in patients intervened by Compound Qingdai Capsule(P<0.05).Conclusion:Compound Qingdai Capsule could improve the skin lesions of patients with advanced psoriasis vulgaris，and its mechanism might be related to shifting Th1/Th2 balance towards Th1.