In order to analyze the effect of in-situ stress on the plastic zone expansion of surrounding rock of rectangular roadway, FLAC3D software was used to simulate the plastic zone distribution of rectangular roadway under different burial depth. Assuming the ideal geological and mining mechanics environment, four groups of in-situ stress numerical models were established to analyze the influence of burial depth on plastic zone of rectangular roadway. By comparing and analyzing the plastic zone expansion law under different mining depth conditions, it can be seen from the plastic zone map of simulation results that the plastic zone basically presented circular distribution. With the increase of burial depth, the damage area in the middle of roadway surface and the top and bottom angles expanded evenly, the plastic zone expansion range increased, with the increase of coal seam burial depth, the surrounding rock expanded range. The growth rate slowed down, and the plastic zone did not change with the depth increasing in the two sides. It could be concluded that with the increase of burial depth, the extension range of plastic zone of surrounding rock expanded in a negative exponential form, and the variation tended to zero at last.