Abstract: This paper systematically calculates the influence range, peak value and peak position of abutment pressure of this face, and verifies that the abutment pressure has “mining thickness effect” by the methods of theoretical calculation, FLAC^3D numerical simulation and field measurement in non-uniform thickness of coal seam in 15081 top-coal caving face in Jiulishan mine.The results show that the change of abutment pressure is not just related to the thickness of one time mining seam, and to the change rate of coal thickness in a certain range.It not only provides a theoretical basis for guiding safe coal caving in working face, but also provides a new idea for studying abutment pressure.