Teaching English at university in Vietnam, it is necessary for the lecturer to build a language environment in the classroom and avoid explaining meanings in Vietnamese so that students have many opportunities to listen to English, learn pronunciation, think and express ideas in the target language. Working in this way, they can develop both their language competence and language performance and partly avoid negative influences of their mother tongue on the second language. The lecturer can satisfy the requirement of teaching and fulfill his/her duty by making use of students' knowledge of other subjects to show the meaning of new word explicitly and correctly. This is an integration in teaching, a viewpoint which has existed for a long time in the world, but is not largely applied to teaching a foreign language in Vietnam. If the teacher uses it, he will change his traditional way of teaching and motivate his students to brainstorm, imagine, and enhance the training quality. The article ends with an example of teaching the text "Where in the world" taken from the New Cutting Edge series, using the viewpoint of integration.