Abstract: Roof of 4#coal seam in Jiulong Colliery ,Fengfeng Mining Area is hard wild-limestone of 3.5m thickness, and the floor is thick aquifuge combined with thin limestone and Ordovician limestone. Since 4# coal seam being mined, some water inrush accidents from floor Ordovician limestone have occurred. In order to analyze the mechanism of floor water inrush on condition of hard roof and thick aquiclude, a mechanical model of floor failure is established based on zero position failure theory to analyze the influence of roof pressure transfer on the failure depth of floor, and the mechanical criterion of confined water lifting is given based on fracture mechanics. In view of the fact that there is thick water resisting layer in the coal seam floor, and the traditional underground floor reinforcement and even regional treatment still can not completely eliminate the Ordovician limestone water inrush, the full cycle treatment technology of floor water disaster is proposed. To evaluate the treatment effect , three-dimensional detection of trinity combined with floor verification hole, working face water inflow and Ordovician limestone water level is utilized. The study has shown that firstly, the hanging roof area is large and the periodic pressure is strong, which leads to the increase of floor damage depth under the condition of hard roof. Combined with the effect of stepped lifting of water conducting, it is easy to occur delayed water bursting. Through the pre mining area treatment, the coal seam floor is comprehensively reinforced to eliminate the disaster inducement factors. During mining, the weak area of coal seam floor is mainly reinforced to achieve water reducing mining. After mining, the water retaining mining is realized by reinforcement. The full cycle treatment mode of Ordovician limestone water disaster is established. After the treatment, there is no hydraulic connection between the thin and Ordovician limestone. The Ordovician limestone water level and the water inflow of the working face floor change with the periodic pressure, but the change range is small. The water inflow of the working face is only 0.46 ~1.12 m³/min, and the treatment effect is well. The results have some significance for the prevention and control of Ordovician limestone water inrush on condition of hard roof and thick aquiclude in North China Coalfield.