Abstract: Objective To construct normal values of body mass index(BMI)for assessing child and adolescent's overweight and obesity.Methods BMI centiles of children aged 0-18 years were calculated by using LMS method.The centiles for children aged 18 years that reached adult's cut-off point(25,30kg/m²)were used as normal value for child and adolescent's overweight and obesity.Results Age-specified BMI normal values for children's overweight and obesity assessment were given,they were smaller than those recommended for international use and other countries,this indicated that children's physique in Shanxi was slim,and the nutrition statues was not so good as that of developed countries and areas.Conclusion Age-specified BMI normal values presented in this paper can be used to assess child and adolescent overweight and obesity in Shanxi province.