To investigate the feasibility and load-bearing stability of using soilbags to support expansive soil slopes, a field test was conducted on an expansive soil slope supported by soilbags. The physical and mechanical properties and stability changes of the soilbag slope protection structure during the slope loading process were analyzed. In addition, numerical unconfined compression tests were performed to investigate the reinforcement effect of the soilbags. The results indicate that, at the macroscopic level, soilbags exhibit good impermeability and water-retention performance under normal rainfall conditions. The swelling pressure generated by expansive soil after moisture absorption significantly affects the pressure between the bags. The filling ratio and degree of compaction during construction have substantial effects on stability. A slope protection structure with a high filling ratio and a low degree of compaction is prone to sliding collapse under extreme climatic conditions, whereas its flexibility prevents further collapse. At the mesoscopic level, during loading, the soilbags reinforce the soil inside the bags through stress coordination. The soil in the bottommost bag first reaches the critical failure state, and the side of the bottommost bag ruptures first. The subsequent loss of soil particles from the bag causes the stacked soilbags to slide, leading to the formation of a slip surface and the collapse of the upper soilbags.