The bus-based distributed structure has been applied to the field of drones because of its simple structure, easy expansion, and maintainability. The research group takes unmanned helicopter as the research object, and carries on the technical upgrade on the basis of the original centralized flight control system. A design scheme of distributed flight control system based on CAN bus is proposed. It describes the overall design scheme, hardware design, communication mechanism, software development and implementation of distributed system based on CAN bus, and carries out semi-physical simulation verification. The test results show that the actual bandwidth occupied by CAN bus is 10.5%, and there is no frame loss. The synchronization accuracy of communication reference clock is less than 150 μs, which can fully meet the requirements of flight control system. Through the whole process of flight semiphysical simulation, it is proved that the distributed flight control system based on CAN bus can meet the real-time, reliability and other control requirements of unmanned helicopter flight control system, and the design meets the engineering requirements.