A principal is the supreme leader of a school engaging in both administrative and academic affairs. In terms of leadership, however, a principal is often regarded as having focused more on administration rather than the instructional leadership. After the education reform in these years, principals' instructional leadership has been increasingly valued in the current educational environment of Taiwan, and has become popular issues in education administrative research. As far as the number of current dissertations and theses is concerned, plenty of results has been accumulated. This study analyzed and explored the situations of principals' instructional leadership from 1996 to 2010. Through the study of the issue, the researcher hopes to find out the current status of principals' instructional leadership and further probe the future trend of them. Based on the study's findings, recommendations are proposed for future studies.