In recent years, with continuous breakthroughs in information technologies, especially artificial intelligence, communication, and intelligent computing, intelligent unmanned swarm has been developing rapidly. Intelligent unmanned swarm system, with its advantages of low cost, strong adaptability to harsh environments, no risk of human casualties, and high efficiency in task execution, is being widely applied in fields such as smart grids, smart logistics, and autonomous driving. At the same time, the customization of swarm systems has become a significant constraint on its development. This paper proposes an open, extensible swarm system architecture. It begins by defining key terminologies and describing the core characteristics of intelligent unmanned swarm system; Then progresses to a conceptual model; Subsequently, the article introduces the reference model, describing it from entity-based and domain-based perspectives; Building upon these reference models, the paper delves into a detailed refinement from three views: functional reference architecture, network reference architecture, and deployment reference architecture, providing a comprehensive reference architecture for the advancement of intelligent unmanned swarm systems. This work can be used as a groundwork for the standardization of architectural practices in the realm of intelligent unmanned swarm systems.