Objective: To understand the pubertal development of primary and secondary school students in urban and rural areas of the Inner Mongolia Autonomous Region in 2021, so as to provide clues for further clarification of the health hazards of early pubertal initiation. Methods: From October to November 2021, primary and secondary school students in 12 provinces and cities of Inner Mongolia were selected by stratified cluster random sampling, including 21 662 girls who had reached menarche and 10 600 boys who had their first seminal emission, as well as 46 183 girls who had not reached menarche and 78 995 boys who had not experienced their first seminal emission. The height and weight of the primary and secondary school students were measured, and the time of first seminal emission or menarche was recorded. The study used the Mann-Whitney U test to analyze the differences between urban and rural students, Spearmans rank correlation to analyze the correlation between overweight and obesity and the age of pubertal initiation, and the Logistic regression model to analyze the correlation between pubertal initiation and age of pubertal initiation. Results: The age of menarche for urban girls [(12.31±1.29) years old] was earlier than that of suburban girls [(12.43±1.24) years old], and the age of first spermatozoa for urban boys [(13.85±1.20) years old] was statistically significant compared with that of suburban boys [(13.79±1.36) years old] (t=12.76, 10.58, P<0.05). There was a negative correlation between the age of menarche and overweight/obesity among girls aged 10-14 years (r=-0.169, P<0.05), and there was no statistically significant correlation between the age of spermarche and overweight/obesity in boys aged 5-9, 10-14, and 15-20 years (r=0.122, -0.022, -0.004, P>0.05). The occurrence of menarche in overweight girls was 1.06(95%CI=1.01-1.11) times higher than that in the normal group, and 1.13(95%CI=1.06-1.20) times higher among obese girls than normalweight girls. Compared to urban areas, primary and secondary school students in suburban counties observed the onset of puberty later [OR=0.88(95%CI=0.85-0.91) for menarche, OR=0.94(95%CI=0.89-0.99) for first spermatozoa] (P<0.05). Conclusions Obesity during childhood and adolescence is associated with earlier onset of puberty among female students in Inner Mongolia, and later onset of puberty among primary and secondary school students in suburban counties compared with those in urban areas.