Objective To investigate the clinical efficacy of modified Buzhong Yiqi Decoction combined with conventional drug therapy in the treatment of stable chronic obstructive pulmonary disease (COPD), and determine the effect on respiratory muscle and lung function in the patients. Methods A total of 120 patients with stable COPD admitted in our hospital from August 2015 to August 2016 were prospectively enrolled in this study. They were equally and randomly divided into the treatment group (Buzhong Yiqi Decoction+Seretide Evohale) and control group (Seretide Evohale). After the treatment of 8 weeks, the predicted percentage of forced expiratory volume in one second (FEV1%), ratio of FEV1 to forced vital capacity (FEV1/FVC)) were used to evaluate the pulmonary function parameters of each group before and after treatment, and the score of the activity of accessory respiratory muscles and the Medical Research Council dyspnea scale (MRC) were employed to assess the respiratory muscle strength of the patients. Statistical analysis was performed using SPSS 16.0. Results After the treatment, when compared with the control group, Buzhong Yiqi Decoction group had obviously lower scores in cough, expectoration, gasp, spontaneous sweating, colds, shortness of breath and wheezing (P<0.05), significantly higher predicted FEV1% [(57.92±6.09) vs (52.84±6.64), P<0.05] and ratio of FEV1/FVC [(67.34±7.11) vs (63.01±6.95), P<0.05], and notably lower MRC [ (1.38±0.39) vs (1.61±0.49), P<0.05] and accessory respiratory muscle activity score[ (1.41±0.41) vs (1.79±0.50), P<0.05]. The total efficiency was higher in Buzhong Yiqi Decoction group than the control group (95.00% vs 81.67%, P<0.05). Conclusion Modified Buzhong Yiqi Decoction combined with conventional drug therapy can improve lung function, relieve respiratory muscle fatigue, and thus promote the clinical efficacy in the stable COPD patients.