From 1980 till now, ”teacher leadership” become school leadership's important research topic in light of western educational reform, scholars wrote a lot of it and considered it can enhance teacher learning communities, teaching reform, students' skill and achievement, positive school culture and teacher professionalism, etc. Barth(2006) proposed the concept of teacher leadership is an idea whose time has come, because that places school leadership in a single role, the principalship, this traditional leadership view is not conformed to today's school leadership. However, research of teacher leadership is still in its infant stage in Taiwan. First of all, the article introduces the intension of teacher leadership. Secondly, it explores the definition and the theoretical foundation of teacher leadership. Finally, the functions of the teacher leader will be explored and suggestions for every educational staff as reference.