This longitudinal study aimed to explore whether distinct developmental trajectories of body mass index (BMI) would be predictive of diabetes risk in general Chinese adults.A total of 4,519 participants aged >18 years who were free of diabetes in 2011 (baseline of the current analysis) were enrolled in this study. All participants completed a medical examination every year during 2011 to 2016, and BMI levels were measured two to six (average: 5.6) times. Group-based trajectory modelling was applied to identify BMI trajectories over time. New-onset diabetes was confirmed in 2016.During 2011 to 2016, four distinct BMI trajectories were identified according to BMI range and changing pattern over time: "low" (19.6%), "moderate" (33.4%), "moderate-high" (33.4%), and "high" (13.6%). 168 (3.7%) new-onset diabetes cases were confirmed in 2016. Compared with "low" BMI trajectory, participants in "high" BMI trajectory were at significantly higher risk for new-onset diabetes (adjusted relative risk [RR] 3.24, 95% CI 1.27-8.24). Notably, BMI trajectories based on the first four or three annual BMI tests yielded similar results. By contrast, no significant correlation was found between categories of baseline BMI and new-onset diabetes in 2016 after multivariate adjustment.Our results indicate that distinct BMI trajectories, even identified using only four or three annual BMI tests, are significantly associated with new-onset diabetes. Monitoring BMI trajectories over time may provide an important approach to identify sub-population at higher risk for diabetes. This article is protected by copyright. All rights reserved.