Objective: To analyze Internet behaviors of children and adolescents and their influencing factors, and to provide scientific basis for health education guidance and prevention measures. Methods: A stratified cluster sampling method was used. From January to June 2019, 30 955 primary school students in 16 provinces (municipalities), from eastern, central, and western economic zones of China were selected to conduct a questionnaire survey, regarding general demographics, diet and exercise, tobacco, alcohol and sleep, Internet and electronics usage, etc. Results: Among them, 43.1% of students had never been online with girls (44.7%) higher than boys (41.8%)(χ2=21.04, P<0.01); 1.3% of students reported online time for more than 4 hours a day, boys were significantly higher than girls(χ2=15.87, P<0.01); Internet addiction was detected in 2.4% of elementary school students, with boys (3.0%) higher than girls(1.7%)(χ2=331.77, P<0.01), and the trend increases with grade. With sixth grade (3.3%) were significantly higher than children from the first grade (0.8%) and other grades(χ2=163.96, P<0.01). Children’s tendency to Internet addiction was 11.9%, of which boys were 13.0% and girls were 10.6%, boys were significantly higher than girls(χ2=117.66, P<0.01). Pearson correlation analysis revealed that, after controlling gender age, boarding school, family relationship, single parents and regrouped families, smoking, drinking sugary drinks, eating fried foods, and left-behind were positively related to Intenet addiction(r=0.06, 0.07, 0.27, 0.44, 0.07, 0.11, 0.09, P<0.01), while medium and high intensity sports, effective physical education, health education in school, AIDS education and parental restrictions on TV and computer games, were negatively associated with internet addiction(r=-0.74, -0.65, -0.04, -0.05, -0.63, P<0.01). Conclusion The internet addiction of Chinese primary school students is common and increases by year. High-intensity, high-density sports, effective physical education, and health education could help prevent Internet addiction among children.