Objective: To investigate the associations between childhood obesity and performance of six minute walk test (6MWT), providing evidence for exercise tolerance assessment and exercise intervention strategies for children and adolescents. Methods: From March 2021 to December 2023, a cohort study was conducted among students recruited from a primary and secondary school in Chongqing, a total of 709 valid samples were included. The 6MWT was used to assess exercise tolerance, with vital signs measured before and after the test. Anthropometric indicators, including height, weight, and waist circumference, were measured using standardized procedures. Generalized additive models (GAM) and restricted cubic spline (RCS) regression were employed to analyze the nonlinear relationships between obesity related indicators and six minute walk distance (6MWD). Results: The mean 6MWD of participants was (602.59±70.73)m. GAM showed that after adjusting for confounding factors, body mass index (BMI) and weight had non linear relationships with 6MWD [effective degrees of freedom were 1.55 and 7.13 respectively], and overweight/obesity was associated with a decrease in 6MWD ( β =-18.65) (all P <0.01). Further RCS regression analysis showed that both BMI and weight showed an "inverted U shaped" non linear relationship with 6MWD in the overall population and sex stratified subgroups; the 6MWD of females was lower than that of males, and it showed a significant downward trend with the increase of BMI or weight (all P <0.05). Conclusion Body weight and BMI in children and adolescents have an important impact on 6MWD, and obesity in children and adolescents is markedly associated with decline in exercise tolerance.