Considering that the trapezoidal anti-slide pile side has better bearing performance than the rectangular section anti-slide pile, the reason is that the value of the bottom angle of the section has a direct influence on the bearing performance of the pile side. Based on the conditions of soil arching effect on the pile side, the method of numerical simulation is adopted. The FLAC-3D finite element software is used to establish the contact surface between pile and soil through the contact surface statement, and the displacement change of the pile-soil contact surface is captured. Combined with the displacement of the characteristic horizontal section z=23 of the thrust and the displacement change of the displacement monitoring point on the displacement axis between the pile and the mid-axis of the pile, the influence of the θ value of the trapezoidal anti-slide pile on the soil arching effect is studied comprehensively. The rationality of the range of the side angle θ of the pile section is illustrated, and the reasonable range of the bottom angle of the pile section is obtained. It is proved that the side angle of the trapezoidal pile section is within this range, and the front surface of the pile can be fully utilized. The force performance of the two parts of the pile surface is promoted by the joint force transmission mechanism of the double arch.