Principal of Madrasah Aliyah Darul Muqimin has a democratic leadership type. It is characterized by actions that absorb the aspirations of his subordinates, firm in the act and make decisions, and to accommodate all its forces objectively. One of the headmaster tasks would provide an assessment of the performance of teachers. Teachers are required to prepare in the scope of the pedagogic and professional competence. Among the aspects of competence in question is the activity of designing, implementing, which includes the first activities, main and end, also carrying out the process of formative and summative evaluation. The main problem will be discuss in this paper is how the Role of Principal in Improving Teacher Performance at Madrasah Aliyah Darul Muqimin. This research is descriptive qualitative that using case study approach, explanation give by using descriptive analytic study, reinforced with inductive thinking and understanding of theory, and analysis of quantitative data to explain certain phenomena and aspects. Principal should be able to push the performance of teachers by demonstrating a friendly, close, and full consideration to the teachers, both as individuals and as a group. Positive behavior of Principal can encourage, guide, and motivate all citizens of madrasah to cooperate in realizing the vision, mission, and goals of madrasah.