Great convenience has been brought by the centralized control plane of Software-Defined Network (SDN), but a lot of security risks have been introduced into it as well. In the light of single point failure, unknown vulnerabilities and back doors, static configuration and other security problems of the controller, a secure architecture for SDN based on Byzantine protocol was proposed, in which the Byzantine protocol was executed between controllers and each switching device was controlled by a controller view and control messages were decided by several controllers. Furthermore, the dynamics and heterogeneity were introduced into the proposed structure, so that the attack chain was broken and the capabilities of network active defense were enhanced; moreover, based on the quantification of the controller heterogeneity, a two-stage algorithm was designed to seek for the controller view, so that the availability of the network and the security of the controller view were ensured. Simulation results show that compared with the traditional structure, the proposed structure is more resistant to attacks.