Abstract: The mining stress would cause the roof and floor broken and failure, spaling and roof falling, floor heave of the seam and would cause the mine pressur e bumping and the coal and gas outburst occurred.The site stress measurement and the numerical simulation combined method was applied to study the mining stress distribution law of the fully mechanized coal mining face in the seam with soft roof, soft coal and soft floor in Jiaojazhai Coal Mine. The results showed that the pilot sup port pressure and stress reducing area was at a distance of 0- 12 m in front of the coal mining face, the stress increased area was at a distance of 12- 40 m in front of the coal mining face, the stress stable area was beyond 40 m in front of the coal mining face and the stress concentration coefficient was 1.41 .7.There was a stress red uced area formed within a scope of 0- -14 m of the lateral support pressure area, a stress increased area formed in the scope of 14- -36 m and the stress sable area for med beyond 36 m.the analysis showed that the deformation and failure of the air return gateway in No.51109 coal mining face in Jiaojiazhai Mine was located under the lateral support pressure increased area formed by the above seam mining face.