Abstract: The extraction of coal seam gas by drilling is the fundamental measure of coal mine gas management, however, due to the constraints of coal seam conditions, the drilling process of gas drilling often encounters problems such as jamming and plugging, which affect the hole formation effect of drilling, and then affect the efficiency of gas extraction. In order to minimize the occurrence of jamming during gas drilling, a sodium-based bentonite-based microfoam drilling fluid was developed in this paper to achieve a smooth drilling process.Firstly, the ratio of its main components was optimized, and the best drilling fluid preparation system was determined through orthogonal tests. The experimental results show that the drilling fluid has good foaming performance, remains stable up to 80℃, and has good erosion resistance to coal dust with mass fraction within 10%; the rock chip settling rate characterizes that the drilling fluid has better rock-carrying ability than ordinary water. Finally, the ability of the drilling fluid to carry coal dust at different flow rates and rotational speeds was analyzed by numerical simulation to evaluate the coal dust-carrying effect of the drilling fluid during the drilling process.