At present, the theoretical calculation method, the in-situ test method and numerical simulation method are used to determine the radius of coal seam gas drainage. Determining a reasonable gas drainage radius parameter has important practical significance to improve drainage effect and eliminate the outburst danger quickly. In order to determine the gas drainage parameters of Huoerxinhe 3# coal seam reasonably and eliminate the prominent risk of mining face quickly and efficiently, the current embarrassment of determining the gas drainage radius was analyzed. Based on the own gas and geological conditions of Huoerxinhe 3# coal seam, the theoretical calculations, laboratory parameters measured and site measurement were used to investigate the effective drainage radius of Huoerxinhe 3# coal seam. The results show that the site measurement of gas drainage radius has greater difficult in testing, worse precision and other issues. But it can obtain the exact value of effective drainage radius by combining theoretical calculation method with the in-situ test method. The effective drainage radius of Huoerxinhe 3# coal seam is 1.6m by using this method. It can provide the basis for gas drainage borehole design, raise the gas drainage efficiency and ensure the mining safely. Simultaneously, this method in this paper can be used as a general method to determine effective drainage radius.