Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work is financially supported by a Construction Programme of Independent Innovation Ability of Community Health Nursing Engineering Laboratory in Jilin Province (Study code: 2020C038-8) awarded to FL. Background Despite the benefits, patients with coronary heart disease are less likely to engage in physical activity. Gamification is the use of game design elements (such as points, leaderboards, progress bars, and badges) in nongame contexts to increase motivation and engagement. Scientific evidence suggests that smartphone-based gamification interventions have the potential to increase physical activity participation. However, empirical evidence on the efficacy of such interventions among patients with coronary heart disease is still emerging. Purpose This study incorporates behavioral economics into a gamification intervention based on a smartphone app (WeChat applet) to explore whether a gamification intervention can improve participation in physical activity and other related physical and psychological outcomes in patients with coronary heart disease. Methods A group of 108 participants (mean age 53.0+10.5, 18.5% female) with coronary heart disease were randomly assigned to three groups (Control group: WeChat applet+step goal setting; Individual group: WeChat applet+step goal setting+gamification; Team group: WeChat applet+step goal setting+gamification+collaboration). The primary outcomes included the change in daily steps and the proportion of patient-days that step goals achieved. Patients also completed Psychological Needs Satisfaction in Exercise Scale (PNSE), Behavioural Regulation in Exercise Questionnaire (BREQ)-3, Physical Activity Enjoyment Scale (PACES), Generalised Anxiety Disorder (GAD)-7, Patient Health Questionnaire (PHQ)-9 at baseline, 12 weeks and 24 weeks. Results Compared with the control group (n=36), participants in the individual group (n=36) had a significantly greater increase in mean daily steps from baseline during the intervention group (difference 988; 95% CI, 259 - 1717; P<0.01), and had a significantly greater proportion of patient-days that step goals achieved (difference 0.38; 95% CI, 0.04 - 0.13; P<.001), competence (difference 0.6, 95% CI, 0.3 - 0.8; P<.001), autonomous motivation (difference 3.3; 95% CI, 2.2 to 4.4; P<.001), weight (difference -1.2, 95% CI, -1.8 to -0.6; P<.001), BMI (difference -0.4; 95% CI -0.6 to -0.2; P<.001) and waist circumference (difference -1.2; 95% CI -1.7 to -0.6; P<.001). Participants in team group (n=36) had a significantly greater increase in competence (difference 0.3; 95% CI 0.1 to 0.6; P<.001), relatedness (difference 0.9; 95% CI 0.7 to 1.2; P<.001), autonomous motivation (difference 3.0; 95% CI 2.1 to 4.0; P<.001),however, no significant difference of change in step counts was found between team group and control group. Conclusions A smartphone-based gamification intervention may be an effective way to promote physical activity in patients with coronary heart disease within 12 weeks if we incorporate appropriate game elements into the smartphone application.