Abstract: For the pressure relief gas governance problems of "three soft" coal seam fully mechanized working-face, a similar physical simulation and UDEC numerical simulation experiments have been conducted to research the stope fracture evolution law of the face affected by mining.At the same time, the field slating backward water injection method and the field high level borehole gas drainage concentration monitoring method were used to verify the experiment results.The results show that the fractured situation can be observed more clearly when the observation plane is whitewashed in the similar material simulation experiment, and the similar material simulation is basically consistent with UDEC simulation results.The maximum height of caving zone and fractured zone are 12 m and 38 m, respectively, the best vertical distance between the two bores of high level borehole is 20-26 m.Water injection by slating backward at field indicates the maximum height of caving zone and fractured are 10 m and 39 m, respectively.The results of field high level borehole gas drainage concentration monitoring manifests that 1-2 and 1-3 high level borehole gas drainage concentration is the maximum, which vertical distances are 24.4 and 20.5 m, respectively.It also verified the correctness and scientificity of similar physical simulation and numerical simulation experiment methods and results.