Objective To investigate the physical activity pattern of school-age children with autism spectrum disorder(ASD) at different cognitive levels, and explore its association with the weight status. Methods Forty-five children with ASD from the Research Center for Psycho-behavioral Development of Children and Adolescents at SUN Yat-sen University from July 2018 to May 2019 were included. Participants were divided into the high function ASD(HFA) group and the low function ASD(LFA) group, according to their full-scale IQ score assessed by the Chinese Wechsler intelligence scale for children, 4th edition, and clinical interviews from the professional physician. Anthropometric measures were assessed by standard methods in order to calculate body mass index(BMI). After that, participants were asked to wear the Actigraph GT3X+ accelerometers for 7 continuous days. Multiple logistic regression model was used to analyze the association between physical activity and weight status. Results The prevalence of overweight and obesity were 15.6% and 17.8%, respectively. Average daily minutes of moderate to vigorous physical activity(MVPA) was 49.2±20.3, which failed to meet the WHO recommendations(60 min/d). The compliance rate of MVPA was 26.7%. Besides, we found that the LFA group had higher amounts of vigorous-intensity PA(VPA) (Z=2.55, P=0.011) and MVPA (Z=1.98, P=0.048) than the HFA group. Higher levels of moderate-intensity physical activity(MPA), VPA and MVPA were positively associated with the overweight/obesity in the HFA group, even after adjustment for age, gender and average sleep duration(OR=0.09, 95% CI 0.01-0.94; OR=0.06, 95% CI 0.004-0.96; OR=0.06, 95% CI 0.005-0.70, respectively). No significant association was found in the LFA group. Conclusion A high percentage of school-age children with ASD suffer from physical inactivity, overweight, and obesity. There is a difference in the correlation between physical activity and overweight or obesity among children with different cognitive levels, and a negative correlation is found in the HFA group, which can provide a reference for further targeted intervention.