During the development of traditional onboard information service units，it is often necessary to conduct in-depth research and design of various data transmission protocol details.Therefore，each application software of the information service units has to spend a lot of development time on the format processing and type conversion for the protocol data，resulting in low development efficiency.In this paper，an onboard software bus communication middleware based on the publishing-subscription mechanism is designed.Based on the subscription-publishing model，the middleware can provide data distribution services for application software，effectively reducing the temporal and spatial coupling between the data transmission and acquisition nodes.It is compatible with telemetry link protocol，remote control link protocol，in-star high-level bus communication protocol，etc.，and has a simple application program interface，providing excellent convenience for the rapid development and mass production of over 10 types of APP software on the information service units of low-Earth-orbit (LEO) satellite constellations.The actual project application shows that the software bus middleware meets the real-time and flexibility requirements of information exchange for onboard information service unit subsystems，while improving the system development efficiency.