Abstract: The water-inrush from floor inundates Working face 51101W in Liangzhuang coal mine,Xinwen Mining Group.Based on water quality analysis,it is judged that the source is Ordovician limestone.According to the structural characteristics,it is concluded that a spade shape fault,which extends the unconformity boundary between Ordovician and Carboniferous,and whose maximum fault throw is 7 m, is responsible the accident.Combined with engineering practicality,the view of judging water leading fault with fault throw is denied.It is suggested that using the coefficient (S) of fault throw (H) dividing fault incidence angle (α) shows the degree of a fault influencing water inrush.