OBJECTIVE To compare the efficacy and safety between tiotropium capsule and placebo in a 12-week treatment in patients with chronic obstructive pulmonary disease (COPD). METHODS A multi-center, randomized, double-blind, and placebo-control clinical trial was conducted in 205 patients with stable COPD. They were randomized into inhaled tiotropium 18 µg once daily or placebo, lasting for 12 weeks. The spirometry was conducted at baseline, 6 and 12 weeks after treatment. RESULTS A total of 205 patients with stable stage I or II COPD were randomized to tiotropium and placebo groups. The improvement rate of clinical symptom in the tiotropium group was 25.2% (26/103) after a 12 week treatment, but that of the control group was 4.9% (5/102). The forced expiratory volume in one second (FEV₁) and forced vital capacity (FVC) in the tiotropium group increased (0.2 ± 0.3) L and (19.2 ± 29.1)% after the 12 week therapy, but only (0.0 ± 0.2) L and (0.8 ± 18.2)% in the placebo group. The rate of adverse reaction in the tiotropium group was 7.8% (8/103), but in the placebo group was 12.8% (13/102). The difference between the 2 groups was not significant. All adverse reactions were mild, including dry mouth and sore throat. CONCLUSIONS This trial confirmed that tiotropium powder 18 µg once daily relieved dyspnea, prevented aggravation and improved pulmonary function, clinical symptoms and life quality. Tiotropium was a safe and effective once-daily anticholinergic bronchodilator as first-line maintenance therapy in COPD.