Abstract: In order to study the effect of coal seam dip angle on floor pressure relief laws of fully mechanized mining face, through the mechanics theory analysis, it obtains that floor pressure relief depth presents a trend of decreasing as coal seam face angle increasing; using FlAC^3D numerical simulation software, stress distribution characteristics of working face floor with different angle 0°,15°,30°and 45°are simulated, and by making pressure relief coefficient 35% as boundary, different depths of floor pressure relief are obtained, and according to vertical stress and displacement curves of different angle working faces' floor mine rock, floor stress relief and deformation laws are analyzed. Taking gas outburst coal mine as practical engineering background, the correctness of theory and numerical simulation analysis are verified.