Objective: To evaluate the association between nocturnal sleep duration and behavioral problems in Chinese school-age Children, and to provide reference for the development of recommended nocturnal sleep duration for school-age children. Methods: A total of 4 160 school-age children selected through cluster random sampling in Guangzhou urban areas. Caregivers reported children’s behavioral problems and sleep habits using parent version of the Strengths and Difficulties Questionnaire (SDQ) and sleep quality questionnaires. Results: The average nocturnal sleep duration per day of school-age children is (9.07±0.76)h, the proportion of children having slept less than 9 h/d was 46%(1 912). There were statistically significant differences in the distribution of sleep duration among children with different chronotype and maternal education levels(P<0.05). There were statistically significant differences in children’s sedentary behavior duration and nap duration at different sleep duration(P<0.05). The association between children’s nocturnal sleep duration and behavioral problems was typically nonlinear and U-shaped(P<0.05). The inflection points of nocturnal sleep duration for total difficulties, emotional problems, conduct problems and peer problems were 9.65, 9.25, 9.42 and 9.30 h, respectively. Conclusion Nocturnal sleep duration shows a nonlinear association with behavioral problems in school-age children. The optimal range of nocturnal sleep duration for mental health is between 9 to 10 hours and the problems of psychological behavior were the least among school-age children.