In order to study the stability influence of high slopes in rainy climate conditions in southern mountainous areas and the optimization measures for design and construction, relying on the high retaining wall slope reinforcement and reconstruction project within the transition river beach of folded hills, through finite element analysis on the design of slope support structure of typical sections and deformation, and comparison of engineering site monitoring, the time course of deformation of support structure, existing multi-story residential buildings and soil is studied, the relevant regular characteristics of structural deformation are explored, and the joint action mechanism of engineering protection and natural protection is revealed. The results show that, for retaining walls reinforced with anchors and lattice beams, the anchors will bear most of the earth pressure and anchor reinforcement can be carried out directly on the existing retaining walls. At the same time, under the rainy conditions in the south, the use of natural protection and engineering protection can effectively improve the overall stability and safety redundancy of the soil. For the low retaining wall at the foot of the slope, the height needs to be determined in combination with the rock and soil stratification to avoid overall instability caused by rainfall. The results can provide a certain reference for the construction and disposal of similar projects.