Abstract: The question of “how to governance the intellectual assets of platform partners” hasn’t explained in platform-mediate network form the theory. Through the multi-case analysis, this paper discusses the intellectual assets mechanisms in platform-mediate network from the theory of legitimacy. We identify three intellectual assets governance mechanisms, including making the public collective sense, establishing coordination conflict and contradiction and building the identity based new platform governance. The platform leaders use legitimation strategies with other actors give the legitimacy to the partners, in order to encourage the partners or potential partners to innovate. In this paper, the “black box” of intellectual assets of the platform partner governance mechanisms is opened in the platform-mediated network, which reveals the different legitimation strategies and makes clear the relationship between the execution actors of legitimation strategies, the judgment actors and the winner of the legitimacy. Our study guides the platform-mediated network governance in practices and provides the ability of sustainable development for high-speed platform-mediated networks.