Abstract: Objective: To explore the effect of family socio-economic status, family environment and physical activity on children's screen time. Methods: Using the "Assessment of Family Socioeconomic Status, Family Environment, Physical Activity, and Screen Time of Young Children" scale to investigate parents of children aged 4 to 6 years in Chengdu. Results: (1) Family socioeconomic status is positively correlated with family environment and physical activity, but negatively correlated with children's screen time; the higher the socioeconomic status of a family, the richer the family environment, the more frequent physical activity, and the shorter children's screen time; (2) family environment, physical activity and children's screen time are related to children's gender, age, kindergarten geographical location, parents' age and educational background, among which family environment and physical activity play a dual intermediary role in family socio-economic status and children's screen time, and both constitute a chain intermediary; (3) the influence mechanism of family socio-economic status on children's screen time is complex, and there are four effective channels, of which two intermediary channels have the greatest influence, the direct channel is the second, and the chain channel is the smallest, and physical activity is the most important transfer station in these channels. Conclusion: in the influence mechanism of family socio-economic status on children's screen time, family environment and parent-child interaction are important mediators, while physical activity is the most important. Inhibiting children's screen time and improving the level of parent-child interaction is the key to success.