Objective: To analyze the association between physical activity and screen time with overweight and obesity in preschool children, and to provide evidence for childhood obesity prevention and control. Methods: Using a case control study design, 109 overweight or obese children (the case group) were recruited from four kindergartens from a community of Chaoyang District, Beijing, and 117 children with normal weight in the same kindergarten (the control group) were recruited as control. Gender and age were matched between the case and the control group. Univariate analysis was used to compare the demographics, physical activity time, screen time, sleep and diet characteristics between the two groups. Logistic regression was used to analyze the association of physical activity and screen time with overweight and obesity in preschool children with adjustment for covariates. Results: After adjusting for age, gender, average daily sleep time, the total score of Children s Sleep Habits Questionnaire (CSHQ), Chinese diet balance index for preschool children (DBI-C), children with <3 h of daily physical activity had an increased risk of overweight and obesity compared with those with ≥3 h of physical activity ( OR=2.55,95%CI=1.16-5.64，P =0.02), and the risk of overweight and obesity increased with each additional quartile of daily screen time in children ( OR=2.44,95%CI=1.69-3.52, P <0.01). Conclusion Insufficient physical activity and excessive screen time are independent risk factors of overweight and obesity in preschool children. Comprehensive intervention measures should be taken to effectively increase physical activity and reduce screen time for overweight and obesity prevention and control in preschool children.