Abstract： Objective： To observe the clinical effect of Yupingfeng granules combined with acetylcysteine for chronic obstructive pulmonary disease(COPD) with lung qi deficiency syndrome at stable stage，and its effect on the lung function， inflammatory factors，and T-lymphocyte subsets in peripheral blood. Methods：A total of 274 cases of COPD patients with lung qi deficiency syndrome at stable stage were selected and divided into the observation group and the control group according to the random number table method， 137 cases in each group. The control group was given acetylcysteine effervescent tablets， and the observation group was additionally given Yupingfeng granules based on the treatment of the control group. Both groups were treated for 12 weeks. The clinical effect and the incidence of adverse reactions were compared between the two groups. Before and after treatment， the changes in the lung function， the score of COPD Assessment Test(CAT)，inflammatory factors and T-lymphocyte subsets in peripheral blood in serum were observed in the two groups. Results：The total effective rate was 95.6% in the observation group，higher than that of 85.4% in the control group(P＜0.05). After treatment， the percentages of forced expiratory volume in one second to the predicted value(FEV1% pred)，peak expiratory flow(PEF)，and the ratios of inspiratory capacity to total lung capacity(IC/TLC) in the two groups were increased when compared with those before treatment(P＜0.05)， and the scores of CAT were decreased(P＜0.05). After treatment， FEV1% pred， PEF， and IC/TLC ratio in the observation group were higher than those in the control group(P＜ 0.05)，and the score of CAT was lower(P＜0.05). After treatment，levels of tumor necrosis factor-α(TNF-α)，interleukin-17 (IL-17)，and CD8+ in serum in the two groups were decreased when compared with those before treatment(P＜0.05)，and the three levels in serum above in the observation group were lower than those in the control group(P＜0.05). After treatment， levels of CD4 + and CD4 +/CD8 + values in the two groups were increased when compared with those before treatment(P＜0.05)，and the two indexes in the observation group were higher than those in the control group(P＜0.05). The incidence of adverse reactions was 4.4% in the observation group，and 2.9% in the control group；there was no significance in difference(P＞0.05). Conclusion：In the treatment of COPD with lung qi deficiency syndrome at stable stage，the therapy of Yupingfeng granules combined with acetylcysteine can significantly improve clinical symptoms and the lung function. Its mechanism may be related to down- regulation of expression levels of inflammatory factors in serum and rectification of Tlymphocyte subset disorder in peripheral blood.