Objective To investigate the effect of Bushen Peiyuan Capsules on small airway impedance index and structural function in patients with chronic obstructive pulmonary disease (COPD) in deficiency of kidney yang type at stable stage. Methods A total of 300 COPD patients in deficiency of kidney yang type were randomly assigned to control group or observation group, with 150 cases in each group. The control group received routine regimen for treatment, based on which the observation group received oral administration of Bushen Peiyuan Capsules. Both groups received treatment for 3 months. The pre⁃ and post⁃treatment small airway impedance index (R5⁃R20, Fres), tracheal wall thickness (WT), boundary wall thickness (BWT), and WT/BWT value; in addition, the grade 9 bronchial lumen area (9⁃LA), the grade 9 bronchial airway area (9⁃AA), the grade 9 bronchial wall area (9⁃WA), and 9⁃LA/AA, 9⁃WA/AA values, as well as 6⁃minute walk test (6MWT) distance were compared between patients of the two groups. The post⁃treatment Traditional Chinese Medicine symptoms efficacy was compared between patients of the two groups. Results After treatment, the observation group exhibited lower R5⁃R20, Fres, WT, BWT, WT/BWT value as compared with before treatment and the control group, and the control group exhibited a higher R5⁃R20 as compared with before treatment (P<0.05). Both group yielded elevated 9⁃LA and 9⁃LA/AA value, and the observation group was higher than the control group, whereas 9⁃WA and 9⁃WA/AA value were decreased as compared with before treatment, and the observation group was lower than the control group (P<0.05). Both groups expressed a longer 6MWT distance as compared with before treatment, and the observation group was longer than the control group (P<0.05). The observation group depicted a higher total effective rate of Traditional Chinese Medicine symptoms as compared with the control group (P<0.05). Conclusion On the basis of routine treatment, additionally employing Bushen Peiyuan Capsules for the treatment of COPD patients in deficiency of kidney yang type can decrease small airway impedance, relieve small airway wall thickening, alleviate small airway reconstruction, which is worthy of application and promotion.