Chronic obstructive pulmonary disease (COPD) is a disease state characterized by persistent airflow limitation and associated with an accelerated decline in lung function, impaired quality of life, hospitalization, and increased mortality. As a major public health problem, COPD is predicted to rank as the fifth burden of diseases in the world by 2020. Thus, prevention of exacerbations is a important goal in the management of COPD. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) Scientific Committee launched a joint project in 1998. Its goals were to raise awareness of COPD and to improve prevention and treatment of COPD patients around the world. In the 2017 GOLD guidelines, inhaled long-acting bronchodilators, including inhaled long-acting muscarinic antagonists (LAMAs) and inhaled long-acting beta-agonists (LABAs), are recommended for the management of all stable COPD patients. However, it is not known whether LABA or LAMA will be more effective for initial relief of symptoms in patients with GOLD A/B COPD. In this multicenter, randomized study, the investigators evaluate the efficacy of formoterol(LABA) and tiotropium(LAMA) in the treatment of patients with GOLD A/B COPD. The primary endpoint is postbronchodilator FEV1, and the secondary endpoints include the frequency of COPD exacerbation, other lung function parameters, CCQ score and mMRC/CAT score.

Inclusion Criteria:

Clinical diagnosis of group A or group B stable COPD. Must be able to inhale Formoterol or Tiotropium.

Exclusion Criteria:

Asthma. Cystic fibrosis. Bronchiectasis. Lung cancer. Glaucoma. Tachyarrhythmia or other serious heart diseases. Prostatic hyperplasia.