Abstract: This study explored the relationships of loneliness, peer acceptance, problem behaviors, and family functioning based on investigation of 246 3rd~5th graders. The results showed: Children's externalizing problem behaviors mediate the relationship between family functioning and peer acceptance. Peer acceptance is the mediator of the relationship between externalizing problem behaviors and loneliness. Internalizing problem behaviors mediate the association of family functioning and loneliness. As the other indirect pathway, externalizing problem behaviors and peer acceptance orderly mediate the effect of family functioning on loneliness. Furthermore, family functioning has strong effect on loneliness directly. Finally, the reasonability and constraint of these mediating roles were discussed

Key words: loneliness, peer acceptance, problem behaviors, family functioning, mediating effect