Code-switching between English and Chinese usually occurs in students' talk when they are involved in taking communicative language activities in college English class. This paper studies the situations in which students are likely to use codeswitching and analyzes it from the perspective of the mental world in Verscheren's Adaptation Theory. It shows that inadequate mastery of English language, cultural differences and the improper adjustment to context may lead to students' using of codeswitching. It also shows that the use of code-switching in students' talk adapts to students' cognitive elements and emotive elements as well.
