This paper aims to explore the application of discourse knowledge in oral English classroom activities. Through the detailed analysis of relevant theories and practical teaching cases, this paper holds that the effective application of discourse knowledge can significantly improve students' oral and communicative abilities, and help them communicate more naturally with language. Specifically, discourse theory not only helps students understand the coherence and cohesion of language, but also enhances their ability to use language in real situations. On this basis, this paper puts forward some concrete teaching strategies and methods, such as role playing, group discussion and oral presentation and other diversified classroom activities, to stimulate students' learning interest and provide more practical opportunities. In addition, two practical teaching cases are used to demonstrate the application and effect of discourse knowledge in oral English teaching. This paper hopes that these suggestions can provide useful reference for oral English teaching, so as to promote the all-round development of students' language ability.