According to the relative variable trend of slope displacement after its construction, this study declared the definitions of the relaxation zone and pre-compression zone, which are collectively referred to as the influenced zone. The construction process of the multi-stage slope was simulated through a large-scale model test. Meanwhile, the concept of the overlapping effect of influence zone was proposed. If the excavation relaxation zones (or pre-compression zones) of lower slope overlapped with pre-compression zones of the upper slope, it would produce relaxation (or reinforcement) effect on the soil and rock of the overlapped zone which belongs to the upper slope. As a result, the force of retaining structure in the overlap zone was influenced. Furthermore, it is found that the wider the overlapped region was, the stronger influence was. However, the overlapping phenomenon had no effect on retaining structures outside the overlapped region. Therefore, the reason for the force change of retaining structure was essentially caused by the overlapping effect in the influenced zone.