Abstract: As the increasing economic developments in China, the reinforcements of large-size slopes are frequently encountered during the constructions of hydraulic and hydroelectric power, transportation, mining, and national defense projects. Three main factors influencing the choice of slope reinforcement methods, are chosen to be slope dimensions, engineering geological conditions and project importance, and classified by three grades. It is analyzed that present slope reinforcement methods have some limitations and defects for the reinforcement of important slope characterized by worse engineering geological conditions. For this reason, the authors have developed a new reinforcement method, i.e., underground beam-pile frame structure system. This system is applicable to the reinforcements of large-scale slopes. By connecting adjacent piles and beams, a spatial frame structure will be constructed. The slope parts with a lower stability can be closely jointed with stable rock masses in depth. This is helpful for exerting the self-sustaining capacity of the rock masses. Not only existent tunnels (e. g. investigation adits, testing tunnels) can be utilized for constructing the structure system, but also drainage and monitoring for slopes can be easily and efficiently realized.