The invention discloses a multirate and multichannel downlink telemetry data combining and splitting processing system and method. The system includes an asynchronous scheduling unit and a synchronousscheduling unit. The asynchronous scheduling unit includes a plurality of splitting modules. Each splitting module includes a buffer receiving module, a primary splitting module, a to-ground cache module, and a relay cache module. The buffer receiving module receives a plurality of downlink telemetry data transmitted by computers within a satellite and transmits the downlink telemetry data to theprimary splitting module. The primary splitting module carries out splitting processing on the downlink telemetry data according to a downlink channel, and sends the downlink telemetry data to the to-ground cache module and the relay cache module. The synchronous scheduling unit is used for combining and splitting the downlink telemetry data in the to-ground cache module and the relay cache module. The system and method solve the problem of multichannel downlink telemetry data combining and splitting and independent switching rate.