Abstract: Taking a typical coal seam floor as the research subject and based on field test data, this study investigates the effective drainage radius and gas emission reduction performance of conventional through-layer boreholes (ø94 mm, ø113 mm) and directional long boreholes (ø96 mm, ø120 mm) under different drainage modes. Three-dimensional gas flow models for both conventional through-layer boreholes and directional long boreholes were established using OpenGeoSys(OGS) software to analyze gas pressure and gas flow velocity during drainage. By integrating numerical simulation results with field test data, a comprehensive analysis was conducted on the influence of different borehole diameters and drainage methods on coal seam gas drainage efficiency, as well as the effects of various drainage methods and factors on the time required to meet the drainage standard. The results indicate that under the same drainage conditions, the larger-diameter conventional through-layer borehole (ø113 mm) can shorten the pre-drainage time by approximately 20 days compared with the ø94 mm borehole. The drainage efficiency of directional long boreholes is significantly superior to that of conventional through-layer boreholes. Specifically, the ø120 mm directional long borehole achieves an effective drainage radius of 6 m after 234 days of pre-drainage, reducing the pre-drainage time by 30 days relative to the ø96 mm borehole. Gas pressure and drainage negative pressure exert a considerable influence on the efficiency of reaching the gas drainage standard for conventional through-layer boreholes, whereas coal seam permeability has a greater impact on that for directional long boreholes. Moreover, simulation results indicate that directional long boreholes require considerably less time to meet the drainage standard than conventional through-layer boreholes.