The invention provides a satellite-borne high-speed multi-load data transmission baseband system. The system comprises a solid-state memory, a data processor and a high-speed serial port cable, the solid-state memory is connected with the data processor; the high-speed serial port cable is connected with the solid-state memory; multiple paths of load data are input into the solid-state memory through the high-speed serial port cable; the solid-state memory can complete operations of data caching, data reading, data recording and data erasing; the solid-state memory and the data processor markchannel identifiers according to an internal protocol, and multi-path load data combination to four-path ground data transmission channel downloading or multi-path load data combination to any two-path data transmission channel downloading is completed under the condition of not increasing data format overhead. According to the invention, the bottleneck problem of the interface processing capability of the data processor when satellite multi-load high-speed data is input into the baseband system is solved, and the reliable and flexible baseband system for recording and storing the multi-load high-speed data and routing and transmitting the multi-load high-speed data according to a transmission channel is realized.