Abstract：Objective：To observe the clinical effect of modified Erchen tang combined with routine western medicine for chronic obstructive pulmonary disease(COPD) at stable stage. Methods：A total of 86 cases of patients with COPD at stable stage were randomly divided into the study group and the control group according to the envelope method，43 cases in each group. The control group was treated with routine western medicine， and the study group was additionally treated with modified Erchen tang based on the treatment of the control group. After three months of treatment，the clinical effect，the improvement of curative effect of lung function and immune function in the two groups was compared. Results： After treatment， the total effective rate was 93.02% in the study group and 76.74% in the control group， the difference being significant(P＜0.05). After treatment，the values of FEV1，FEV1/FVC and FEV1% in the two groups were all increased when compared with those before treatment(P＜0.05)，and the above indexes inf the study group were higher than those in the control group(P＜0.05). Before treatment，there was no significant difference being found in the comparison of the levels of CD3+，CD4+，CD8+ and CD4+/CD8+ between the two groups(P＞0.05). After treatment，the levels of CD3+，CD4+ and CD4+/ CD8+ of immune function in the study group were improved when compared with those before treatment(P＜0.05)，and the levels were higher than those in the control group(P＜0.05)；CD8 + in the study group was decreased when compared with that before treatment(P＜0.05) and lower than that in the control group(P＜0.05)； in the control group， there was no significant difference being found in the comparison of the levels of CD3 + ， CD4 + ， CD8 + and CD4 +/CD8 + before and after treatment(P＞0.05). Conclusion：The therapy of modified Erchen tang combined with routine western medicine for COPD at stable stage can effectively improve the clinical symptoms and lung function of patients as well as enhance the immune function，whose curative effect is better than that of simple western medicine.