The behavior of Top Management Team leaders is a critical factor to influence both the team and the organization’s performance .However, the current articles are insufficient in revealing the effect which leadership behaviors exert on group performance. Based on system theory and IPO theory, this article presents the theory model of TMT leaders’ behavior exerting effect on team’s performance. Using case research method and targeting the public department’s senior executive group as the research objective, it reveals the inherent system of leadership behaviors’ effect on team performance .By concluding and coding and recognizing the key variables among leadership process, it verifies and modifies the theory model. The research shows that the leader group’s behaviors affect team performance through variables such as team process, team members and team environment etc; besides, every variable has effect on each other. This article tries to provide theory guidance for the managers to create high effectiveness & performance senior executive group and improve the theory research of leadership behaviors’ effect on team performance.