Individual learners' affective factors are very important for foreign language learning. In China foreign language learning mainly happens in the classroom. Foreign language teachers are the organizers and carriers of language classes, and thus they inevitably influence the students' affection. This study explores how EFL teachers influence students' affect, what the teachers should do to develop and make good use of students' positive affect, and what the teachers should do to avoid the negative affect and facilitate its possible transformation into the positive. (Contains 10 tables.)