The purpose of this study was to gain a better understanding of children's peer conflicts in elementary school, the characteristics of their developing peer relationships, and factors which affect children's peer relationships, as well as to explore intervention strategies for improving peer relationships. Semi-structured interviews, lasting around 60 minutes, were conducted with 9 elementary school teachers. The data was analyzed using grounded theory. The results showed that factors affecting children's peer relationships included inability to identify the problem of children's peer relationships, domestic violence, and extreme parenting attitudes. Being self-centered, blaming others, introversion, and aggression impaired children's peer relationships. Peer conflict situations in school included being isolated from subgroups, frequent pestering and arguing, lack of social skills, and difficulties cooperating with others. Intervention strategies for improving peer relationships included enhancing family functions and school systems. Creating a parent-teacher working alliance, improving parent-child relationships and enriching parenting information could improve family functions. Promoting a sense of group belonging, clarifying the issue of conflict, strengthening social skills, and increasing empathy could improve school systems. Characteristics of the proper expression of ideas, leadership, kindness, altruism, and contribution to their groups improved children's peer relationships. Suggestions for future research were also put forward.