【Abstract】Input interaction and output， all of them are important for the language learning. This assertion has pedagogical implication for our College English teaching.
　　【Key words】Input； Interaction； Output； English teaching Textbook
　　1. Introduction
　　Children can develop their language without effort， but why are we still struggling in the foreign language classroom？（Meisel， 2011）. Both teachers and students complain it a lot and desire to find a way out. Given the importance of input， interaction and output in the process of learning a second or foreign language， this paper is going to review the roles of input， interaction and output in the second （foreign） learning and then analyze its pedagogical implication for the College English teaching.
　　2. Input， interaction and output in SLA
　　Krashen （1982， 1985） proposes the Input Hypothesis， which believes that exposure to “i 1” is sufficient to guarantee acquisition. Swain （1985， 1995） argues that Krashen oversimplifies considerably the processes of acquisition， and downplays the role of output and proposed the Output Hypothesis to emphasize the status of output in SLA. In regard to the study of the Interaction Hypothesis， it is the interaction （negotiating for meaning） that helps realize the comprehensible input and output and connects them as a whole because what the learners should master includes both declarative knowledge （know what）， and procedural knowledge （know how） （Gass