OBJECTIVES: To analyse the relationship between prevalence of diabetes and Body Mass Index (BMI) and the distribution of people with diabetes among different BMI categories in Chinese adults. METHODS: Systematic review was conducted in China National Knowledge Infrastructure (CNKI) from 2006 to 2012. “Diabetes” and “BMI” were used as keywords. Inclusion criteria were studies that reported diabetes prevalence according to BMI categories. Exclusion criteria were studies that population were not adults or sample sizes were less than 1000. Underweight, normal, overweight and obesity were defined using the recommended Chinese BMI cut-off points of <18.5, 18.5-24, 24-28, >=28. Non-linear regression in STATA was used to analysis the relationship between prevalence of diabetes and BMIs. Prevalence of diabetes were adjusted from existing data which was conducted according to WHO’ BMI classification criteria (<18.5, 18.5-25, 25-30, >=30) to meet Chinese BMI criteria, based on two nationwide representative studies of Yang et al. and Chinese Center For Disease Control And Prevention (CDC). Numbers of people with diabetes among BMI categories were calculated based on Chinese population. Sensitivity analysis was conducted. RESULTS: Twenty-three articles were selected, 8 of them met the eligibility criteria. Prevalence of diabetes increased with BMI and exponential regression model fit best. Yang et al. reported the prevalence of diabetes were 4.5%, 7.6%, 12.8%, 18.5% according to WHO’s definition of underweight, normal, overweight and obesity respectively. The prevalence of diabetes were estimated to be 4.50%, 7.26%, 11.53%, 15.95% after adjusting by Chinese definition. Therefore, Chinese adults with diabetes were estimated to be 4.35 million, 35.13 million, 35.70 million and 19.36 million respectively. Sensitivity analysis showed the non-linear regression model was robust. CONCLUSIONS: Prevalence of diabetes increase exponentially with BMI. Approximately 55 million adults with diabetes are overweight and obesity in China. Body weight control should be a priority in the prevention and management of diabetes.