Abstract: Objective To analyze vital capacity weight index of 1 806 elementary school students from Haidian District,Beijing in 2014,and to provide references for improving children and adolescents' health level. Methods The cluster random sampling method was used to sample 1 806 elementary school students from Haidian District to measure their height,weight and vital capacity.The vital capacity weight index was calculated by using the formula[Vital Capacity/weight(ml/kg)].The t-test was used to compare the differences of vital capacity and vital capacity weight index between the boy group and the girl group in different age groups.Chi square test was used to compare the differences in underdeveloped rate and excellence rate.BMI value was calculated according to formula[weight/height²(kg/m²)],and the students was divided into light weight,normal weight,overweight and obesity based on corresponding standards.The difference in vital capacity weight index was compared among the groups with different BMI value. Results A total number of 1 806 elementary school students were enrolled into this study,which included 923 boys and 883 girls.The absolute vital capacity of both in boys and girls in generally increased with the age.Among the same age group,the vital capacity of boys was larger than that of girls and the difference was statistical significant(except for the age group of 10 years old),P<0.05.The difference in vital capacity weight index between boys and girls was significant in 6,7 and 9 years old groups(P<0.05),but not in 8,10 and 11 years old groups(P>0.05).The underdeveloped rate of girls was higher than that of boys(8.4% vs.5.1%),P<0.05;but the excellence rate was not significant(11.5% vs. 13.4%),P>0.05.The vital capacity weight index was negatively correlated with the BMI,and the vital capacity index declined prominently with the increase of BMI. Conclusion The physical function in lightweight and normal weight groups is superior to that in overweight and obesity groups,which indicate that overweight and obesity affect physical healthy development to some extent;the vital capacity weight index will decline with the increase of weight.