【Objective】 To investigate the current prevalence of overweight and obesity among children and adolescence in Xi'an urban area. 【Methods】 13 994 students with 7~18 years were investigated prevalence overweight and obesity using random cluster sampling method.The overweight and obesity were defined with according to body mass index(BMI) criteria.Cubic smoothing spline was used to directly calculated weight,height and BMI of children and adolescents aged 7~18 years in Xian urban.P₅₀ of weight and height,P₈₅ and P₉₇ of BMI were compared to China standard curves in 2005. 【Results】 The incidence of overweight children with 7~18 years was 10.42%,those of boys and girls were respectively 11.85% and 8.83%.The incidence of obesity children with 7~18 years was 4.67%,those of boys and girls were respectively 4.92% and 4.40%.The centile curves of P₅₀ of weight for boys and girls,height for girls were similar with that of China standardization curves height and weight of children with 0~18 years in 2005.The centile curves of P₅₀ of height for boys with 10~15 years was a little lower than those of China standardization curves.The centile curves of P₈₅,P₉₅ of BMI for boys were similar with that of China standardization curves.The centile curves of P₈₅,P₉₅ of BMI for girls below 14 years were similar with that of China standardization curves, but that of after 15 years was a little lower than China standardization curves. 【Conclusions】 The incidence of obesity students with 7~18 years in Xi'an doubled within 17 years.The effective precautionary measures of overweight and obesity among children and adolescence are the necessary tideway of the situation.