Abstract：Gas extraction effective radius is the basic parameters and important basis of borehole layout parameters,it is important to determine accurately to save drilling of quantities,improve the efficiency of gas extraction and realize the gas extraction standard. In order to confirm gas extraction effective radius,from the definition of effective radius and the influence of radius,the determination methods of effective radius are discussed,and the existing problems of various methods are analyzed. Finally,it is pointed out that effective radius of gas extraction should be determined by using theory analysis,numerical simulation and field practice based on multiphysics coupling. The next research focus should be the building of coupling model based on elastic-plasticresearch damage and thermal-hydro-mechanical coupling model,and development of quick measurement technique and portable equipment for testing gas extraction effective.

Keyword：hole drilled along seam;gas extraction;effective radius;gas pressure;