The distributions of stress and displacement fields at different depths in coal seam floor were simulated using numerical simulation software FLAC3D,and the maximum failure depth and the most easily damaged position in coal seam floor in mining process were found out.The results showed that numerical simulation can more comprehensively reveal the stress fields,deformation and failure characteristics,and failure range and depth of rock mass in coal seam floor under mining,these are favourable to select and optimize design mining scheme and reduce the testing time,so improve the economic and social benefits of mine.