Abstract: Objective To investigate weight perception and associated factors among primary and middle school students in urban Chongqing,and to provide scientific basis for obesity related health education and psychological intervention.Methods Stratified cluster sampling method was used to select 2 798 primary and middle school students in urban Chongqing.Questionnaire survey and anthropometric measurements (height and weight) were conducted.Results The prevalence of overweight and obesity of the primary and middle school students was 22.9%,boys (27.6%) was significantly higher than girls (17.8%) (x2 =24.210,P <0.01).More than a quarter of students (30.5%) showed discordance between weight perception and actual BMI.Low consistency was found between body self-perception and BMI,kappa was 0.418 and 0.403 for primary and middle school students,respectively.Multi-logistic regression analysis showed that boys(OR=1.497,95%CI=1.239-1.809),students with low family economic status (OR=1.827,95%CI:1.340,2.492) and high paternal education level (OR=2.855,95%CI=1.053-7.741) were more likely to underestimate body weight than peers.Middle school students(OR =1.932,95% CI =1.411-2.646),girls(OR =2.558,95% CI =1.854-3.531),poor family relations (OR=2.468,95%CI=1.324-4.600),and those from low-income households (OR=1.967,95%CI=1.131-3.422) were more likely to overestimate.Conclusion Obesity is prevalent among students in urban Chongqing.Monitoring adolescents' perceived weight in addition to their BMI is critical to understanding the challenge we face with childhood obesity.