In the teaching situational contexts, the teacher talk and the instructional pragmatics are related but different in the instructional register. Teacher talk is characterized in language expressions and principles of teacher talk, and in contrast, instructional pragmatics can be manifested as attitudes and strategies of using language in teaching. This thesis sets forth the respective characteristic of the teacher talk and pragmatic usage in the situational contexts of instruction, and reveals the problems of inappropriate expressions, fossilizing teaching behaviors and inadequate human care from the view of Cooperative Principle, Politeness Principle, Relevant theory and Adaptation theory. And the thesis claims that the teachers should be enhancing the instructional pragmatic awareness, implementing the student-centered principle and respecting students' life values by talking appropriately, realizing the optimized relevance in teaching and learning, and insuring the reasonable adaptation in teaching process in accordance with students' learning needs.