An offloading method, of a satellite-to-ground edge computing task, assisted by a satellite and a high-altitude platform can offload a computing task of a ground user equipment (GUE) to a low earth-orbit satellite (LEO SAT), to meet a computing requirement of the GUE and to reduce latency and energy consumption. The method includes four main steps: 1. The GUE selects an associated high-altitude platform. 2. The GUE uses multi-input and multi-output (MIMO) transmission to offload the computing task to the high-altitude platform. 3. The high-altitude platform may also use the MIMO transmission to offload the computing task of the GUE to the LEO SAT. 4. The high-altitude platform and the LEO SAT cooperate to process the computing task of GUE, and reasonably allocate a computing resource to reduce energy consumption; and in MIMO edge computing, the GUE or the high-altitude platform uses the same time-domain and frequency-domain resource.