Abstract: Based on the engineering practice that the gully landform has a great influence on the mine pressure appearance in the stope, taking the 12309 working face of Wangjialing coal mine as the research object, using the method of theoretical calculation and similar material simulation, this paper studies the influence law of the gully surface on the rock fracture angle.Based on the theory of elasticity and rock mechanics, the mechanical model of rock beam fracture angle is established, and the theoretical formula of rock beam fracture angle including rock beam fracture angle α, rock beam bearing load q, rock beam tensile strength R_T and rock friction angle φ is derived.With the increase of the tensile strength R_T, the fracture angle α increases in the form of logarithmic function.With the increase of rock load, the fracture angle decreases in the form of quadratic function, and the range of fracture angle is about 60°-70°.Similar material tests show that the stress at the bottom of the valley is greater than that at the top of the slope, the cracks are more developed in the mining stage of the uphill slope, and the subsidence of the key layer is large, and there is stress concentration at the bottom of the valley.At the same time, the rationality of the calculation formula of the fracture angle is verified by similar simulation tests.