Politeness embodies human civilization,acting as one behavioral criterion of moral significance to maintain the harmonious personal relationships.Politeness Principle,an essential research topic in pragmatics,is greatly meaningful in people’s daily communication.It is also needed in English class which involves the communication between teacher and students.With a theory basis of Politeness Principle put forward by Leech,this paper explains the content of Politeness Principle and probes into the application of Politeness Principle in English class teaching,citing the application of Tact Maxim,Approbation Maxim,Modesty Maxim and Agreement Maxim as examples to suggest that pleasant class atmosphere,good relationships between teacher and students,enthusiasm,politeness awareness and communicative competence can be obtained when the teacher observes Politeness Principle. Politeness embodies human civilization, acting as one behavioral criterion of moral significance to maintain the harmonious relations of peoples. Politeness Principle, an essential research topic in pragmatics, is greatly meaningful in people’s daily communication. Is also needed in English class which involves the communication between teacher and students.With a theory basis of Politeness Principle put forward by Leech, this paper explains the content of Politeness Principle and probes into the application of Politeness Principle in English class teaching, citing the application of Tact Maxim, Approbation Maxim, Modesty Maxim and Agreement Maxim as examples to suggest that pleasant class atmosphere, good relationships between teacher and students, enthusiasm, politeness awareness and communicative competence can be obtained when the teacher observers Politeness Principle.