Abstract: Based on the two phase flow principle, the drilling technology of pneumatic conveying slagging was theoretically research in soft and outburst coal seam. The bigger the resistance to flow is, the more pressure losses, so it is very necessary to reduce flow resistance. The influencing factors of flow resistance are analyzed and discussed, and on basis of this solutions are put forward with reducing "internal resistance" and decreasing "external resistance". The calculation and analysis indicates that the flow resistance is greatly reduced while increasing the bore diameter of drill pipe joint, reducing the steep angle of joint and optimizing structure parameters of helical blades.