The Shiliushubao landslide is one of the giant landslides with complex structure in the Three Gorges Reservoir area. Since the dam was filled with water, the landslide has shown signs of revival, causing loss of life and property to several people around. In order to study the deformation failure mode and response mechanism of Shiliushubao landslide under the fluctuation of reservoir water level, the large-scale physical model test was used to accurately control the fluctuation condition of the experimental reservoir water level, and the displacement sensor, earth pressure sensor and pore water pressure were embedded in the slope. The sensor was used to analyze the experimental phenomenon. The results show that the influence of the reservoir water level fluctuation is mainly concentrated at the foot of the front edge of the landslide, and the rapid decline of the reservoir water level has a significantly greater effect on the landslide deformation than the increase of the reservoir water level; The mechanical response of the slope body has a hysteresis, and the effective soil stress increases when the reservoir water rises, the anti-sliding force of the sliding belt increases, and with the increase of the rising rate, the penetration force directed into the slope is larger, which is conducive to the stability of the landslide; Under the condition of the reservoir water level, the deformation and failure mode of the Shiliushubao landslide is sorted as: original slope → Erosion and erosion expansion at the foot of the slope → formation and expansion of the fissure at the foot of the slope → formation of the fissure on the slope surface → local slump, which is a hydrodynamic pressure landslide. The test revealed the deformation mechanism under the condition of reservoir water level, and provided a reference for the study of similar landslides.