In view of the gas extraction problem of No.3 coal seam in the west well area of Sihe Coal Mine, this paper determines the effective extraction radius of coal seam extraction boreholes in combination with the development and mining of coal seam and gas occurrence. The advantages and disadvantages of gas pressure method and gas reserve method are discussed. The effective extraction radius is determined by gas reserve method. The results show that the extraction radius is 10.1 m when the extraction time is 270 d, and the mathematical model of extraction days and effective extraction time is established. A two-dimensional single-hole gas extraction physical model was established by COMSOL software to simulate and analyze the extraction process. It was found that the simulated effective extraction radius was similar to the results of the reserve method, and the longer the extraction time was, the larger the effective extraction radius was, and the gas pressure around the borehole gradually decreased with time.