Objective：To analyze the association between obesity and age at spermarche among Chinese Han boys aged 11-18 years . Methods：The height, weight and status of the spermarche of Chinese Han boys aged 11-18 years were selected from the data of 2010 National Physical Fitness and Health Surveillance．The body mass index (BMI), prevalence of spermarche in each age group and ages at spermarche by BMI groups were calculated. Chi square test was used to analyze the differences of prevalences of spermarche among the boys with different BMIs across ages. U-test was used to compare the differences of age at spermarche between the boys who were obese and not. Results: In the boys aged 12 and 17 years in urban areas and boys aged 13 years in rural areas, the differences of prevalences of spermarche among the normal weight, overweight and obesity groups were significant (P<0.05). The age at spermarche in the obesity group (13.90 years) was 0.1 years earlier than that in the nonobesity group (14.00 years) (P<0.05).Conclusion:Obesity may make the age at spermarche ahead of time.