Objective To investigate the overweight and obesity of primary and middle school students in Sijing area of Shanghai from 2020 to 2022,so as to provide scientific basis for the intervention of childhood obesity.Methods In October 2020 and October 2022,all primary and middle school students in Sijing area underwent physical examination by cluster sampling method.A cross-sectional study was conducted to investigate the obesity and overweight in primary and middle school students of different ages and genders in Sijing area.Results In 2020 and 2022,7 766 and 10 594 students completed physical examination,respectively,and 4 626 of them underwent two consecutive physical examinations.The incidences of overweight and obesity were 15.14%and 21.89%in 2020,respectively.The incidences of overweight and obesity were 15.41%and 21.11%in 2022,respectively.There were no significant differences in the incidences of overweight or obesity between 2020 and 2022(P>0.05).In 2020,the incidences of overweight and obesity of male students were 14.91%and 24.70%;the incidences of overweight and obesity of female students were 15.40%and 18.80%,respectively.In 2022,the incidences of overweight and obesity of male students were 15.04%and 24.14%;the incidences of overweight and obesity of female students were 15.82%and 17.82%,respectively.There was no significant difference in the overweight rate between males and females(P>0.05).The incidence of obesity of male students was significantly higher than that of female students in both 2020 and 2022(P<0.05).In the students aged 12 years old,the incidence of obesity was 27.42%in 2022,which was significantly higher than that in 2020(P<0.05).There was no significant difference in the incidence of obesity between other age groups(P>0.05).Among the 4 626 children who participated in two consecutive physical examinations,the overweight/obesity rates were 14.46%/21.25%in 2020 and 16.04%/21.78%in 2022;there was significant difference in the overweight rates(P<0.05),while no significant difference was found in obesity rates(P>0.05).Among the 4 626 children,there were 2 402 boys and 2 224 girls.In 2020,the overweight/obesity rates were 13.70%/24.48%in these boys and 15.29%/17.76%in these girls.In 2022,the overweight/obesity rates were 16.07%/25.44%in these boys and 16.01%/17.72%in these girls.There was no significant difference in the incidence of overweight between these girls and boys in 2020 and 2022(P>0.05),but the obesity rate of boys was significantly higher than that of girls(P<0.05).Conclusion There are high incidences of overweight and obesity among primary and middle school students in Sijing area of Shanghai,and dietary and exercise guidances should be strengthened.Meanwhile,the incidences of overweight and obesity are higher among boys,and obesity prevention and control measures should be strengthened for boys.