Background: Although overweight and obesity are important risk factors for the physical health of severe mental disorders (SMD), few studies have been reported. Morbidity and mortality associated with physical disorders of SMD can be reduced if detected and managed in the early stages of physical disorders. The objective was to analyse the prevalence of overweight and obesity in patients with SMD and factors associated with sociodemographic and disease characteristics in a cross-sectional population-based study.Methods: This analysis examined prevalence of overweight and obesity of 14,868 managed SMD patients in urban area of Shenzhen city, based on data from the information monitoring system in 2020. Sociodemographical and physiological characteristics of overweight and obesity of SMD patients were described. The multivariate logistic regression models were used to identify the factors associated with the prevalence of overweight and obesity of SMD.Results: Records of 14, 868 participants were included for analysis. The prevalence of overweight and obesity in patients with SMD in this study was 32.6% and 16.1%, respectively. In multivariate analysis, married, Shenzhen household registration, number of years of management 5-10 years and >10 years, participation in family physician services, taking clozapine or aripiprazole, FPG>6.1 mmol/L, hypertension, TC≥5.2mmol/L, TG≥1.7mmol/L, the more frequent the number of follow-ups in the past year were associated with higher odds of overweight and obesity, while older, having tertiary education, and mental retardation with mental disorders had lower odds of overweight and obesity. Compared to their respective reference categories, living status with parents, spouse and children, taking risperidone, aripiprazole, amisulpride and perphenazine, FPG>6.1 mmol/L, hypertension, TC≥5.2mmol/L, TG≥1.7mmol/L, the more frequent the number of follow-ups in the past year were associated with higher odds of obesity, while having tertiary education and schizophrenia had lower odds of obesity. Conclusions: We observed a high prevalence of overweight and obesity with SMD in this study. The findings highlight the need for integrated management of overweight and obesity risk factors among patients with SMD.