Abstract: In view that drainage for decreasing water pressure was useless to guarantee safe mining threatened by water inrush from Ordovician limestone in Feicheng coalfield, the feasibility study of grouting reinforcement of Ordovician top was carried out．Based on the statistics of exploratory boring data, coal mine drilling construction, X-ray diffraction of limestone samples, and microscopic thin section analysis, the macro and micro characteristics of Karst fissure in the Ordovician top of Feicheng coalfield were obtained．The result shows that the optimal depth for grouting reconstruction in Feicheng coalfield is about 20 meters below Ordovician top．Taking LW101002 in Caozhuang coal mine as test object, the grouting reinforcement project for Ordovician top was carried out．The conclusion validity is proved by the comparison of geophysical exploration and drilling before and after grouting．Practice proves that safety mining on the aquifer with high-pressure can be achieved by grouting reinforcement of Ordovician top.

Key words: Ordovician limestone, Karst fissure, grouting reinforcement, water inrush