The paper focuses on the changes of the macro institutions affecting power structure at elementary and junior high school in Taiwan with the viewpoints of historical institutionalism. Research findings include: 1. Macro institutional change relating to school power structure can be divided into three stages; 2. The critical juncture of the original path happened because of the factors inside and outside the original institutions and the strategic actions actors adopted; 3. The change of the macro institutions can be explained by legitimation and power; 4. School power structure now is an interactive one which allows different actors to have more room to take strategic actions, but it may differ because of the regulations from the county level; 5. The operation of the formal institutions is influenced by actors and informal institutions. At last, suggestions for restructuring school power structure, future researches, and school leaders are brought out.