Abstract: To solve the problems of poor ventilation condition and low mining efficiency in the mining of steeply thick seam, according to the condition of steeply thick seam in a mine, a single roadway sublevel caving mining method which combines theoretical analysis with field test is proposed. Along the coal seam boundary, two mining areas are arranged along the boundary of the coal seam to go up the mountain and one mining roadway is mined. In the process of mining, a “herringbone” air return roadway is maintained along the roof side of the roadway in the mining process. As the hydraulic support of caving coal goes forward, the air return lane of the lower section is maintained, so as to form a complete mining area production system. The results of the study show that the mining method reduces the rate of roadway excavation, improves the ventilation condition of the working face, and improves the coal output and the recovery rate is more than 87%. The production capacity of working face is up to 0.18 Mt/a, which meets the safety and high efficiency production demands of the mine.