Based on a typical gently inclined red-bed slope along the Desui expressway, an indoor slope model was established according to the geological analysis and similarity theory. The excavation test was used to simulate the actual engineering slope cutting, and the deformation evolution process of the slope was studied. The results show that the longitudinal red-bed slope with a gentle dip angle of 20° presents a typical tensile-slip failure under the condition of slope cutting. The displacement of the slope increases with the cutting grades, and the horizontal displacement is higher than the vertical displacement. The displacement near the slope surface is larger than the other parts of the slope. The slope deformation is mainly composed of unloading deformation in the cutting slope stage and creep deformation in the stationary stage, and the unloading creates the basic condition for the development of creep deformation. From the uncut slope to the weak mudstone stage, the magnitude and rate of unloading deformation are higher than the creep deformation stage. After the cut slope to the weak mudstone interlayer, the unloading deformation of the slope is lower than the creep deformation. The stress near the cutting slope surface is obviously disturbed while the stress in the middle and trailing edge of the slope is less disturbed by cutting. The overall stress decreases inside the slope, indicating gradual stress release with the slope cutting process. 