In traditional configurations where Low Earth Orbit Satellites (LEOs) are used in conjunction with ground multi-antenna terminals to create a virtual Multiple Input Multiple Output (MIMO) system, the high-speed mobility of LEOs results in an unstable MIMO system topology, which consequently affects the stability of system capacity. This paper introduces two space-ground cooperation modes to enhance the stability of MIMO system capacity. The first method optimizes channel capacity by appropriately allocating the beam power of relay stations, allowing relay stations to achieve transparent forwarding through satellites. The second method involves rotating the angle of the user’s receiving antenna to counteract channel variations caused by changes in satellite positions. Simulation results indicate that both methods can effectively improve the minimum channel capacity, with transparent forwarding offering an enhancement of approximately 22.7%, while the rotational antenna approach can achieve a performance gain of at least 36.3%, even under limited rotation angles.