Rain is one of the main causes of damage to the Ming Dynasty Great Wall in Yuyang borough, Shaanxi Province. This survey show that rain have seriously damaged the site. To study the destructive effect of rain on the sites, the type of damage and the overall impact based on the on-site survey results, the site characteristics, precipitation patterns in the region and the soil erosion theories were analyzed. The results show that damage can be catogorized as either direct or indirect erosion. The main causes of damage are gulch erosion, laminar flow surface erosion and rain erosion peeling. The factors that affect the degree of destruction include the rainfall features, the site shape, characteristics of site soil, the plant growing conditions and the mantle reservoir layer. The main factors affecting each type of damage are different. The research results not only enrich the knowledge of' how rainfall damages sites, but also provide a foundation for the selection of protective actions to be taken for the protection of the Great Wall in Yuyang borough, Shaanxi province.