The process of USV swarm target defense mission is described based on OODA (Observation, Orientation, Decision and Action) ring, and the architecture model of USV swarm target defense mission is studied according to DoDAF (Department of Defense Architecture Framework) operational viewpoint and modeling language SysML. It is proved that the method proposed by this paper can optimize the top-level design of USV swarm target defense mission architecture, and facilitate the understanding and communication of researchers in different fields to the top-level mission.