Abstract: In order to determine the pressure-relief zone width in 27021 return airway of a coal mine, we analyze the pressure relief zone forming mechanism and simulate relief zone change laws with the depth of the tunnel excavation by FLAC^3D software, and explore the deformation mechanism of roadway during the tunneling process, and obtain the coal roadway and roadside deformation influence range with the change of time. And based on the field test of drilling cuttings weight per meter, the width of the pressure-relief zone obtained by numerical simulation is verified according to the drilling cuttings method, and the pressure relief zone width of the two sides of the tunnel is 6 meters.