The current study explored the role of teacher-child relationship plays on the relationship between preschooler's shyness level and externalizing problem. The sample consisted of 463 children from 6 preschools of Shandong province in northern China. Mothers reported the shyness level, aggressive behavior, and attention problem of their children, whereas teachers rated the teacher-child relationships. Among the results, the shyness level of girls were significantly higher than that of boys; children's age was significantly and negatively correlated with parents' rating of child shyness, aggressive behavior, and attention problem; shyness was associated with more aggressive behaviors, more attention problems, higher teacher-child dependence, higher teacher-child conflict, and lower teacher-child closeness. The aggressive behavior was associated with higher teacher-child dependence and higher teacher-child conflict. Teacher-child closeness moderated the relationship between shyness and externalizing problem (including aggressive behavior and attention problem). Teacher-child dependency moderated the relationship between shyness and aggressive behavior.