Cooperative navigation technology has become one of the research hotspots for unmanned swarm systems in satellite denial environments, as it enhances the navigation and positioning capabilities of unmanned swarms. Starting from the connotation of unmanned swarm systems, this paper summarizes the development of existing navigation technologies. Subsequently, it further introduces the current development status of cooperative navigation technology in satellite-denied environments, including cooperative navigation data fusion architecture, navigation and positioning methods in denied environments, and research progress on optimization algorithms for cooperative navigation in unmanned swarm systems. Finally, the paper analyzes and prospects the current problems facing cooperative navigation.