Objective To explore the influence of physical exercise on social anxiety of left-behind children in rural areas， verify the mediator and moderator role of perceived social support. Methods From October to November 2019， 292 left-behind children in rural areas were investigated by the physical exercise rating scale， perceived social support scale（PSSS） and social anxiety scale for children （SASC）， and the data were analyzed. Results The score of physical exercise in rural left-behind children was 1.32±0.59， the score of social anxiety was 6.79 ±4.31， and the score of perceived social support was 54.18 ±14.48. The physicalexercise had significant effect on social anxiety of rural left-behind children（r=-0.211， P<0.01）， while the exercise time， intensity and frequency had significant negative effects on social anxiety （r=-0.219， -0.069， -0.093， all P<0.01）. The perceived social

support had significant effect on social anxiety（r=-0.227， P<0.01）， while family support， friend support and other support had

significant negative effects on social anxiety（r=-0.168， -0.199， -0.203， all P<0.01）. The perceived social support played mediator and moderator role between physical exercise and social anxiety of left-behind children in rural areas. Conclusion The perceived social support has a positive effect on reducing social anxiety and participating in physical exercise of left-behind children. It is suggested that special attention should be paid to the effect of perceived social support in the process of mental health education

and school physical education of rural left behind children.

Physical exercise, Social anxiety, Perceived social support, Mediator and moderator role