The invention relates to a space application communication platform based on a rail retaining last stage of a carrier rocket. The space application communication platform comprises a satellite adapter, an instrument mounting plate, an attitude control system sensor, an actuator, a storage battery, a power control unit, a task manager, a communication relay load and a solar panel, wherein the communication relay load comprises an antenna and an information processing device, the actuator comprises a counterforce flywheel, a magnetic torque and an attitude control exhaust pipe, the satellite adapter is of a hollow circular truncated cone structure with two open ends, and the instrument mounting plate is mounted at a bottom end of the circular truncated cone structure. According to the communication platform provided by the invention, the surplus carrying capacity of the carrier rocket is fully excavated, any necessary devices necessary for realizing an expansion task are deployed in the structural cabin segment of the satellite adapter by the ideas of loading and restructuring, the communication relay load is loaded, high-rail, middle-rail and low-rail space cloud communication service systems for commercial aerospace are constructed to realize measurement and control, communication and other directional services without secondary launching costs, thereby having the advantages of low-cost operation.