The severity grading of chronic obstructive pulmonary disease (COPD) is mainly for the grading of the condition of patients in the stable stage, and is divided into four groups according to the comprehensive assessment of the patients, namely, groups A, B, C, and D. Patients in group A have mild symptoms, low risk, and the pulmonary function classification is generally in grades 1-2, with ≤1 acute exacerbation in the previous year. patients in group B have low risk, many symptoms, and the pulmonary function classification is in grades 1-2 with ≤1 acute exacerbation in the previous year. group C has a high risk, few symptoms, and pulmonary function classification in grades 3-4, with ≥2 acute exacerbations in the previous year. Patients with high risk, few symptoms, pulmonary function classifications in grades 3-4, and ≥2 acute exacerbations in the previous year.Patients in group D with high risk, many symptoms, pulmonary function classifications in grades 3-4, and ≥2 acute exacerbations in the previous year. The choice of medication for treatment varied depending on the severity of the patient.