Abstract: The gas emission of 4301 fully mechanized working face in Xiagou Coal Mine in extra thick and high-gas seam is large,and gas drainage technology in high level gas drainage roadway is affected by many factors when solving this problem,there are two most critical parameters,namely the horizontal distance between the high level gas drainage roadway and the return air roadway,the vertical distance between the roof of the coal seam.In order to seek the optimal values of the key parameters,based on the law of overburden rock mass failure properties in mining,using the method of FLUENT numerical calculation to simulate the influence of the vertical distance and the horizontal distance on the drainage effects,obtaining the optimized parameters after comprehensive analysis of simulation results and field data.The results show that when the horizontal distance is 20 m and the vertical distance is 30 m,the effect of gas drainage in high level gas drainage roadway is the best;after the high level gas drainage roadway in 4301 fully mechanized working face arranged by the optimal value,the average gas extraction in high level gas drainage roadway is 43.93 m³/min,its maximum can reach 54.75 m³/min,accounts for about 75.6% of the total gas emission,the amount of air exhaust from the original 14.03 m³/min drops to 3.91 m³/min,these data prove that the gas extraction effect is significant.