Abstract: In order to provide a theoretical basis for the deformation, damage and breaking of the lateral roof, based on elastoplastic mechanics and mine pressure theory, considering the plastic strain softening of the foundation, a two-parameter elastoplastic foundation beam model along the lateral base is established. The difference curve method is used to solve the deflection curve equation of the beam and the variation law of roof deflection, bending moment and basic reaction force is analyzed. The results show that: when the stress deformation problem of the roof is analyzed, the elastic foundation beam model will lead to some errors between the partial results and the actual situation; after considering the basic plastic softening model, the deflection of the foundation beam increases, and the peak of the basic reaction force declines, the peak position shifts to the deep part, and the result is more in line with the actual situation; the peak position of the load is an important factor affecting the deflection, bending moment and foundation reaction force of the foundation beam. The distance between the peak bending moment and the coal wall increases linearly with the increase of the distance between the peak load and the coal wall before the basic roof breaking. When the roadway width changes, the influence of the coal pillar width on the deflection, bending moment and foundation reaction force of the foundation beam also changes. When the roadway width is 5 m and the coal pillar width is 4 m, the peak deflection and bending moment of the base roof are the minimum values.