Topic: Brief introduction on the role of interaction in early second language acquisitionA. IntroductionVarious hypotheses have been formulated by researchers to study second language acquisition (SLA) in order to benefit the understanding of the language learning process. According to Beller (2008), most hypotheses focus on successive SLA, such as the behaviorist-oriented "contrastive hypothesis", the nativist-oriented "identity hypothesis", as well as the cross-linguistic hypothesis, while few studies paid attention to the SLA of bilingual preschool children. With the increase of immigrants and the importance of SLA considered by bilingual parents, their children tend to learn the second language (L2) along with the first language (L1) at an early stage. Due to limitations in cognition and maturity, children learn language primarily from external environment stimulation created by their parents, educators, and peers. The quality and quantity of linguistic input, functioning as stimulation, interacting with people around children, has a positive influence on children's language learning (Bradley and Caldwell 1976; Clarke-Stewart 1973; McCartney 1984 ; and NICHD 2000). Therefore, it is beneficial for parents and teachers to know how interaction can improve children's English proficiency. Therefore, the purpose of this article is to present the role of interaction in early L2 development and the involvement of children's interaction in education. This article will present the subject from three aspects. In the first part, the literature review will include interaction with parents, teachers and peers respectively. The second part concerns the implications of preschool children's language proficiency. Previous research shows that through interaction with parents, especially mothers, teachers and peers, the grammar, semantics and lexicon of the L2 were improved to a certain extent. Considering the positive effect of interaction on language proficiency, parents and teachers should apply interaction skills in teaching L2 to young children. Parents should pay attention to the use of open-ended questions and adopt different positions to stimulate communication with children, while teachers should focus on creating a context for social interaction to encourage children's verbal interaction with teachers and their peers. However, due to the author's limitations, the significance and methods of interaction cannot be fully presented. The present results may also provide some advice to parents and teachers.