Abstract: The successful use of surface?in?seam (SIS) well in medium coal rank coalbed methane (CBM) of Moranbah field indicates thatSIS wells have the benefits of high productivity, easy operation and broad applicability. Through theoretical analysis and CBM simulation,this paper analyzes the performance between SIS well and horizontal well, and optimizes SIS wells from both production regulation and well design. The result shows that the recovery factor of SIS wells is 2~7 times higher than horizontal wells as the permeability is about 1~40 mD and the gas content is less than 12 m3/m3. Therefore, for the reservoir with low gas content, medium permeability and such a CBM, SIS well is obviously advantageous than horizontal well. When the rational pump displacement of SIS well is about 60~90 m3/d, its downhole pressure should be controlled at about 0.15~0.2 MPa. And when the branch length of the SIS well is about 1 100 m, the optimized branch angle is about 40°~50° and the central axis orientation of SIS well is perpendicular to face cleat, its production performance will be the best