Abstract: The family is the primary context of preschoolers' lives. A positive home music environment is an important pathway for children's music learning and an effective way for them to release and regulate their emotions. A healthy and stable emotional state is the internal foundation for the development of preschoolers' prosocial behavior. Numerous studies from abroad have also shown that the home music environment is conducive to the development of preschoolers' prosocial behavior. To verify the relationship between home music environment and preschooler's prosocial behavior, and to clarify the relationships and internal mechanisms among the variables of home music environment, preschooler's prosocial behavior, preschoolers' musicality and emotional regulation, this study conducted a survey using questionnaires with 1, 201 preschooler and their mothers. The study examined the relationship between home music environment and preschoolers' prosocial behavior, as well as the mediating effects of preschooler's musicality and emotional regulation in this relationship. The results showed that: (1) The home music environment positively predicts preschoolers' prosocial behavior; (2) Preschooler's musicality is an important mediating variable through which the home music environment affects preschooler's prosocial behavior; (3) Preschoolers' emotional regulation ability is an important mediating variable through which the home music environment affects preschoolers' prosocial behavior; (4) Preschooler's musicality and emotional regulation ability play a chain mediating role between the home music environment and preschoolers' prosocial behavior. Based on the mechanisms through which the home music environment affects preschooler's prosocial behavior, the following suggestions are made for parents of preschoolers: Create a home music environment rich in "musicality" to nurture children through music; Emphasize the "emotional" value of music to achieve emotional harmony through music; Cultivate children with rich "musicality" to achieve a harmonious and respectful personality.