Abstract: Taking the serious water inrush accident due to coal mining under super-thick hard igneous rock in Huaibei Mining Group for example, hydrologic and engineering geology conditions of the water inrush are investigated and tested. Based on comparison to the characteristics of other water inrush accidence due to coal mining in home and abroad, a new type of water inrush, named Dynamic Water Inrush, is presented. Hard rock in overlying strata, aquifer or water in bed seperation in roof, dynamic instability happening in the hard rock are the main geologic engineering conditions that result in the Dynamic Water Inrush. The three factors causing Dynamic Water Inrush are water source, water-leading channel and dynamic source. And the forming and interaction of the three factors are the inherent mechanism of Dynamic Water Inrush. The scientific definition of Dynamic Water Inrush are presented based on the compasion of Dynamic Water Inrush with general water inrush. And the oritention of further research of Dynamic Water Inrush are also presented in this paper.