Teaching is the core of education, and educational reform should be carried out on the level of teaching activities. Teachers' performance in teaching is the key to the success of educational reform. Assisting teachers to develop their teaching professions and hence improve their teaching performance is the critical point of current educational reform in Taiwan, and constructing a school-based instructional supervision system is the effective way in helping teachers' professional growth. This thesis first introduces the related concepts of the school-based instructional supervision and teacher's professional growth, emphasizing that instructional supervision is the effective way to help teachers develop their teaching professions, in which a constantly advancing teaching performance is the most important goal. Secondly, this article explains how to construct a school-based instructional supervision system so that teachers' teaching performance can be effectively improved. Finally, this study points out that, in order to assist teachers in their professional growth, constructing a school-based instructional supervision system in Taiwan is necessary and feasible, though it is a tough and long way to go.