In order to analyze the influence of lateral pressure coefficient on the plastic zone expansion of surrounding rock of rectangular roadway, FLAC3D software was used to simulate the plastic zone distribution under different lateral pressure coefficients of rectangular roadway. Assuming the ideal geological and mining mechanics environment, four groups of numerical models of lateral pressure coefficient were established to analyze the influence of lateral pressure coefficient on plastic zone of rectangular roadway. It can be seen that when the lateral pressure coefficient was 0.5, 1.5 and 2.0, the plastic zone expanded elliptically, but when the lateral pressure coefficient was 0.5, the long elliptical axis expanded in the x-axis, the long elliptical axis expanded in the Y-axis and the lateral pressure coefficient was 1.0, the plastic zone expanded approximately circularly; with the increase of the lateral pressure coefficient. With the increase of the lateral pressure coefficient, the extension morphology of the plastic zone gradually transited from the oval of the long axis in the X-axis to the oval of the long axis in the Y-axis, and the extension range gradually increased. It could be concluded that with the increase of the lateral pressure coefficient, the change rate of the damage area increased first and then decreased; with the increase of the lateral pressure coefficient, the change rate of the damage area decreased first, then increased and then decreased; the change rate of the two sides was the same, and increased first, then decreased and then increased.