A diversity of components and their interactions at different levels in classroom constitute a complex and dynamic second language acquisition (SLA) system, whose trajectories reflect the route and rate of learner’s second language development. Based upon Dynamic System Theory (DST), this paper carries on a theoretic study on Classroom Second Language Acquisition (Classroom SLA) by referring to the related research achievements in SLA. Three parts are included in this paper: 1) to construct the theoretic framework for classroom SLA study; 2) to explore the research approaches for Classroom SLA study; and 3) to exemplify the analyses of teacher-students interaction and learner motivation (two popular research domains in Classroom SLA) from DST perspective, with the purpose of providing reference for more follow-up studies.