Loneliness is the dissatisfaction of individual subjective experience with their own social relations, who often feel isolated, sad, empty and desire for the social relations. Loneliness has emerged in preschool age, and showed relative stability across the whole childhood, which is closely related to many adapting problems in the development of children. Family is one of the most important factors affecting the development of preschool children, parent-child attachment as an important part of the family environment, which has important influence on children's loneliness. According to attachment theory, early childhood unsafe parent-child attachment relationships is closely related to a lot of adaptation in later children. In addition to family factors, peer relations is also an important factor that affect children's social adaptation. The children who often suffer from peer rejection are on the edge position in the peer interaction, they also can't get enough social satisfaction and positive emotions from peers, so they are unable to establish a sense of belonging, and leading to loneliness. According to ecological theory, family and peers as the important micro ecological factors affect children’s development, unsafe parent-child attachment relationships may impact children's loneliness through peer rejection. Developmental situation theory think that, preschool teachers as an important adults of children, teacher-children relationships and parent-child relationship exist an interactive effctions on children. Positive teacher-child relationships may have a protective effect to children’s maladaptation,however, conflicted teacher-child relationships may intensify children’s maladaptation.But in the existing study of preschool children, less study focuses on the relations between the above variables are discussed. 193 preschool children(115 boys) from two public kindergartens in Shanghai joined a one-year longitudinal study. In time 1, children with an average age of 4.28±0.31 years old, and mothers completed the parent-child attachment scale, preschool teachers completed the students-teacher relationship scale, using peer nomination to test peer rejection; In time 2 , use the method of children's self-report to collect the data of loneliness. Results show that: (1) the attachment avoidance, peer rejection and loneliness has significant positive correlations; (2) peer rejection plays a mediating role between attachment avoidance and loneliness; (3) the conflicted teacher-child relationship plays a moderating role between attachment avoidance and peer rejection. Relative to the child with low levels of conflicted teacher-child relationships, the children with high levels of conflicted teacher-child relationship may have higher peer rejection and experience higher loneliness. This research adopts interval year longitudinal study design, examines the preschool children's attachment avoidance through peer rejection influence on loneliness, and explored the moderating effect of teacher-child relationships.Understanding the mechanism that the effect of attachment avoidance influence on preschool children's loneliness, helps educators pay more attention to children's intervention and guidance of loneliness from the perspectives of family and the kindergarten.