Based on surface drilling and 14 underground drilling results of Dongpang Mine, the unevenness of Ordovician limestone water richness was found, it decreased as the increasing depth, under Ordovician roof 20～40 m, the water richness was poor. In order to explore water richness features, 29 Ordovician limestone roof grouting drillings were constructed outside the 9201 working face, the result showed that upper the limestone 40 m with poor water richness and permeability, based on the drilling water pressure test result, the upper part is mostly subtle permeable rocks, part of weak permeable was change into water-resisting layer after grouting, ensuring the safe mining of No. 9 coal seam.