Abstract: The water-inrush disasters in karst tunnels are commonly characterized by strong outburst, high water pressure, mass flow and multi-type, and its evolutionary process and dynamic instability is very complex and still unclear.The occurrence condition, criterion and safety thickness of different types of water inrushes are proposed, and the development trend of water inrush mechanism are analyzed in the present study.Firstly, the conception, type and three constituted elements of water inrush are introduced.Secondly, currently research achievements of mechanical mechanism and model, instability criterion and the minimum safety thickness of water inrush are summarized.Finally, the current situation and problems of water-inrush mechanism are analyzed from the point of the three constituted elements.The development trend and research are proposed, including (1) solid-liquid-gas replacement mechanism and energy-releasing pattern of the sources of water inrush disasters, (2) multiphase material migration and evolution law of flow regime in water-inrush passage, (3) dynamic catastrophe mechanism of water-proof structures, and (4) analysis method for simulating the forma tion of water-inrush passage.