Abstract: For the National Key Research and Development Program of China "Research on new prevention and control technology of expansive soil slopes (No. 2019YFC1509800)", the following achievements are obtained: (1) Based on the fractal model for montmorillonite surface and the isothermal adsorption theory, the water-mineral interaction mechanism of expansive soils is revealed, the swelling deformation theory and generalized effective stress theory are established, and the shear strength theory of fractured expansive soils is put forward. (2) The failure mechanism of expansive soil slopes is divided into two types which are controlled by shallow cracks and deep weak planes. The methods to evaluate the stability factor of expansive soil slopes are proposed for two slope failure types. (3) The prevention technology of expansive soil slopes is divided into three types as "separation" technology, "retaining" technology and "stabilization" technology (hereinafter written as SRS for short). The separation technology contains non-expansive clay-covered layer, soil bags, reinforced package and waterproof & drainage layers. The retaining technology contains pile-sheet walls and soilbag retaining walls. The stabilization technology contains anti-slide piles and anchor rods. (4) The standardized design of soilbag, reinforced packages and pile-sheet walls is realized. The application of soil bags, reinforced packages, waterproof & drainage layers and pile-sheet walls are completed for the prevention of expansive soil slopes. The validity of the applied prevention and control technology is checked by the real-time automatic monitoring results in site.