The existing studies on spacecraft focus on improving the networked, intelligent, and autonomous level of avionics systems. This paper reviews the research status of spacecraft avionics system architecture and typical spacecraft avionics system, as well as the technical features and potential trends of key technologies, such as network interconnection, high-speed bus, onboard computing, autonomous operation, and software-defined technology. A development roadmap, a novel kind of intelligent system architecture and application scenarios of avionics systems are then proposed. To tackle the challenges faced in the development of spacecraft avionics systems, suggestions are made from the aspects of system architecture, heterogeneous network interconnection, onorbit intelligent information processing, Commercial Off-The-Shelf (COTS) products application, and intelligent autonomous management. This provides a guide for the related studies on the development of spacecraft avionics technology.