Abstract: In this paper, the water inrush from the floor in south wing roadway of Beixinyao Coal Mine in Ningwu Coalfield is taken as the research object, by analyzing the geological and hydrogeological characteristics of the mining area, comparing the changes in the water level of the Ordovician limestone hydrological observation hole in the area before and after the water inrush, combined with chemical analysis of water inrush, the water inrush source and water inrush mechanism of this mine were studied. The results show that the two water inrushes have similar dynamic processes, and the maximum and stable water inflows are comparable, the time of water inrush coincides with the time of steep drop of water level in the Ordovician limestone hydrological observation hole, the characteristics of the water sample at the water inrush point are basically consistent with the characteristics of the Ordovician limestone water in this area, it is determined that the water inrush source is Ordovician limestone water. The F8 fault cuts the Ordovician limestone aquifer to form a water inrush channel, in addition, the disturbance of roadway excavation destroys the stability of the relative aquifer, the Ordovician limestone confined water overcomes the resistance of structural crack and causes water inrush; the two water inrush points are blocked by the technology of grouting and water plugging with directional borehole, and the floor of the roadway is reinforced by grouting, which ensures the safe excavation of the south wing roadway.