Since 1980s, both the school restructuring abroad and the domestic educational policies have emphasized the importance of educational reform and the change in the principals’ leadership. Most studies of principals’ leadership stressed the trait theory, leading styles, power models and so on. However, there were few studies that adopted cognitive approach attempting to understand what messages and information principals picked up, and how principals’ core belief affected their leading behaviors. In recent years, scholars conducting the viewpoint of cognitive approach pay much attention to these issues and they expect to understand how leaders use their mental models to solve problems of school administration. They want to find out principals' cognition, core belief, and the problem types which principals perceive and deal with behind their leading behaviors. Thus, they can figure out a better way for principals to adjust their leading behaviors. In the studies of principals’ mental models of leadership, we can understand the problems that arisen from educational reform and are closely related to the ecology of the campus. By observing principals’ speeches and behaviors, I investigated how principals use their tacit knowledge, and how they exert influences when managing schools. To complete my study, I invited four junior high school principals recommended by the bureau of education and educational experts to join my project. With their participation, my study attempted to examine how the four principals form their mental models of leadership, and use the models on problem solving. As for the methodology of the study, I collected data mainly from interviews and used short-term observations, documents analysis, and journal reflection to complement my study on the influential factors, content, the operation, and the formative course of mental models of leadership in the four principals. What follows are the conclusions and suggestions of this study. According to the result of my study, conclusions are as follows: 1. The growing-up course and the administrative experiences of principals greatly influence their mental models. 2. The context of school organization influences and limits the operation of principals’ mental models. 3. The completeness in mental model of leadership is the origin of having high-quality influence for principals. 4. The core belief in principals’ mental model of leadership is the key to focus leadership goals. 5. The novice principals rely on personages to get everyday messages, while expert principals rely on experiences and intuitions to get everyday messages. 6. The development of mental model of leadership has three main orientations—the administrative leadership, the curriculum leadership, and the mix of the two. 7. Having habits to reflection is an important key for principals to have high-quality leadership. 8. The model principals have significant influence on principals’ mental model of leadership. On the basis of above-mentioned conclusions, my study proposes some suggestions for the administrative institutions of education, the elementary and junior high school principals, and the follow-up studies: 1. Suggestions for the administrative institutions of education: (1)Enhancing the quality and quantity of workshops of administrative leadership. (2)Encouraging model principals to share their ideals and experiences. (3)Enriching the content of the apprenticeship of principal leadership. 2. Suggestions for the elementary and junior high school principals: (1)Trying to show the mental model of leadership. (2)Making reflection as a habit. (3)Managing personal memory system. (4)Building think tanks and interpersonal networks. 3. Suggestions for the follow-up studies: (1)The theme of study: more exploring the themes of the problem solving, conscious strategies, novice and expert, and type of leadership. (2)The object of study: extending to the schools’ levels, or narrowing the object to the small groups' leaders. (3)The method of study: strengthening the observation of field and informal interview, or adopting the study of grounded theory. (4)The ethics of study: having enough communication with participants of study and revising our study approach or attitude at any time.