The purpose of this article is to analyze the definition and principles of instructional supervision, and to introduce the instructional supervision in England as an example. As a result of this analysis, instructional supervision is defined as a process of inspection and guidance to teaching learning. The purpose of instructional supervision is to improve the quality of teaching and learning. In order to accomplish its purpose, instructional supervision should be implemented by following some principles. The principles are as follows: (1) Instructional supervisior should be professional. (2) Instructional supervisiors should be well organized. (3)Instructional supervision should be implemented in a democratic way. (4) Instructional supervision should be ruled by law. (5) Instructional supervision should be carried out in a variety of ways.