The aim of this study was to evaluate whether a theory-based behavior change intervention could promote changes in physical activity (PA) and sedentary behavior (SB) among patients with chronic obstructive pulmonary disease (COPD), as well as its effects on symptoms of dyspnea, lung function, exercise capacity, self-efficacy, and health-related quality of life (HRQoL). A quasi-experimental design and convenience sampling were adopted. A total of 92 patients with stable COPD were recruited from outpatient and inpatient centers of two hospitals in Zhejiang Province, China. Both the experimental and control groups received standard medical care provided in the hospital. The experimental group performed a PA program based on the behavior change wheel theory. Outcomes were measured at baseline (T0) and after 4 weeks (T1), 8 weeks (T2), and 12 weeks of the intervention (T3). The primary outcome was PA measured by the International Physical Activity Questionnaire (IPAQ). Secondary outcomes included SB measured by the IPAQ, dyspnea measured by the modified Medical Research Council (mMRC) questionnaire, exercise capacity assessed by 6-min walk distance (6MWD), self-efficacy measured by the Exercise Self-Regulatory Efficacy Scale (EX-SRES), and HRQoL measured by the COPD Assessment Test (CAT). In addition, we measured lung function using a spirometer at baseline and 12 weeks. Of the 89 patients included in this study, 64 were male (71.91%), with a mean age of 67.03 ± 6.15 years. At 12 weeks, the improvements in PA, SB, mMRC, 6MWD, EX-SRES and CAT were all statistically significant (P < 0.05) in the experimental group compared to the control group. Repeated measures analysis of variance showed that there were group effects and time effects on total PA, SB, mMRC, 6MWD, EX-SRES, and CAT in both groups (P < 0.001). However, there was no significant difference in pulmonary function between the two groups before and after intervention (P < 0.05). The PA program based on theory significantly increased PA levels, reduced sedentary time, enhanced exercise capacity and self-efficacy as well as HRQoL in patients with stable COPD. Due to the limited intervention time in this study, the pulmonary function of COPD patients may not be reversed in a short time, and the long-term effect of this program on the pulmonary function of patients needs to be further explored.Trial registration: Clinical Trials.gov (ChiCTR2200060590). Registered 05/06/2022.