This study aims to objectively evaluate the clinical efficacy and safety of Traditional Chinese Medicine in the treatment of AECOPD Risk Window, providing a basis for the formulation of TCM treatment plan with AECOPD.

The incidence, mortality, and prevalence of chronic obstructive pulmonary disease (COPD) are high, with a prevalence among people 40 years of age or older of 10.1% worldwide and 13.7% in China. COPD has become the third leading cause of death worldwide. Acute exacerbations of COPD (AECOPD) are important events in the management of COPD because they negatively impact health status, readmission, and disease progression.

Due to the non-random and non-accidental occurrence of AECOPD，with acute exacerbations occurring mainly in a centralized period after an acute exacerbation, and wide open to attack easily in this period, we call this "highly dangerous period" as "AECOPD Risk Window". The AECOPD Risk Window has persistent systemic inflammation and unstable lung function, which increases the risk of AECOPD recurrence and readmission.

At present, western medicine has relatively mature treatment measures for COPD at the acute exacerbation stage and stable stage, however, there is no specific guidance on the medication of AECOPD Risk Window. COPD have been effectively treated with Chinese medicine for a long time. The study of syndrome regularity of "AECOPD Risk Window" provides a basis for the formulation of syndrome differentiation plan.

This is a multi-center, randomized, double-blind, controlled trial to compare the efficacy of two therapies for patients with AECOPD Risk Window. 336 subjects will be randomly assigned in a 1:1 ratio to experimental group or control group for 8 weeks treatment and 18 weeks follow-up. On the basis of health education and conventional treatment, the experimental group will receive TCM granule according to the TCM syndrome, while the control group will receive TCM placebo granule according to the TCM syndrom. The primary outcomes are acute exacerbation rate in the AECOPD Risk Window, COPD Assessment Test (CAT) in the AECOPD Risk Window; and secondary outcomes are time to the first acute exacerbation, degree of acute exacerbation in the AECOPD Risk Window, acute exacerbation rate in the follow-up period, degree of acute exacerbation in the follow-up period, COPD Assessment Test (CAT) in the follow-up period, lung function, clinical symptom scores, mMRC, quality of life and index of security.

Inclusion Criteria:

1. A confirmed diagnosis of AECOPD Risk Window;
2. Age ranges from 40 years to 80 years;
3. Syndrome differentiation meets criteria of qi deficiency and internal cold fluid syndrome, qi and yin deficiency and unclean phlegm heat syndrome, or lung and spleen qi deficiency and phlegm-damp amassing in lung syndrome;
4. Without participations in other interventional trials in the previous one month;
5. With the informed consent signed.

Exclusion Criteria:

1. Pregnant and lactating women;
2. Dementia, mental disorders and reluctant partners;
3. Complicated with heart failure (NYHA Class IV), or Serious cardiac arrhythmias, or unstable hemodynamics;
4. Current respiratory disorders other than COPD (e.g., bronchiectasis, active tuberculosis, pneumothorax, Pleural effusion, pulmonary thromboembolic, or Neuromuscular diseases affect respiratory movement function);
5. Complicated with serious hepatic and renal diseases (liver cirrhosis, portal hypertension, bleeding of varicose veins, dialysis, or renal transplantation);
6. Bedridden for various reasons;
7. Allergic to the used medicine.