Abstract: In the light of concrete data collected from hydrographic holes and inspection holes for overlying layers,as well as the regional data of the study area and the southern Tengxian coalfield,the Quaternary weathered zone,the hydrogeologic and engineering geologic properties of seam top are fully analyzed. Based on study results,the plan of cropping coal pillar leaving and underground water control is put forward.The upper mining limit of Seam No.3 is determined,as result the coal reserve is increased and the life of the mine is extended.