Objective To develop the first barriers to physical activity scale in patients with coronary artery disease (CAD) post-percutaneous coronary intervention (PCI) in China, test its reliability and validity, and use the scale to investigate the influencing factors of physical activity barriers in patients after PCI. Methods Based on the biopsychosocial model, the scale was designed through discussions of multidisciplinary experts at home and abroad. After prediction adjustment, 45 CAD patients after PCI were randomly enrolled from Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine. The internal consistency of the scale items was evaluated by Cronbach's α coefficient, and the test-retest reliability was evaluated by intraclass correlation coefficient (ICC). On this basis, 189 CAD patients after PCI were included for validity analysis, and Spearman correlation analysis and one-way analysis of variance (one-way ANOVA) were used to examine whether the number of comorbidities was a factor affecting physical activity participation. Results There were 20 items in the scale. They reflected the patients' physical activity barriers from 3 dimensions (biological, psychological, and social dimensions). The reliability study included 42 patients, the overall Cronbach's α coefficient was 0.915, and the Cronbach's α coefficients of biological, psychological and social dimensions were 0.825, 0.881 and 0.833, respectively; the overall ICC was 0.877 (95% confidence interval[CI] 0.782-0.932), and the ICCs of the 3 dimensions were 0.710 (95% CI 0.521-0.833), 0.798 (95% CI 0.654-0.886), and 0.821 (95% CI 0.691-0.900), respectively. The validity study included 189 patients, and exploratory factor analysis showed that the cumulative variance contribution rate was 52%; confirmatory factor analysis showed that the fitting model was good and the discrimination validity was ideal. The age of 189 patients was (66.69±8.70) years old, the scores of the 3 dimensions were 18.95±4.34, 24.63±6.38, and 11.49±3.65, respectively, and the total score was 55.07±11.68. Spearman correlation analysis showed that the number of comorbidities in patients after PCI was positively correlated with their scores of the scale (r_s=0.189, P<0.01). One-way ANOVA showed that patients with 3 or more comorbidities had significantly higher scores of the scale than patients with no comorbidity, 1, or 2 comorbidities (P=0.01, 0.03, 0.05). Conclusion The barriers to physical activity scale in patients with CAD post-PCI has good reliability and validity. It can be used as a tool to evaluate the barriers to physical activity in post-PCI patients and provides evidence for specific education in clinical work. The more comorbidities the patients have, the more physical activity barriers they have. Post-PCI patients with 3 or more comorbidities have the highest level of barriers to physical activity, and they are the main intervention group of clinical education.