［Purposes ］ Seepage erosion -type water inrush in karst cavities is one of the typical types of water inrush in karst tunnels，which is not only controlled by the distribution of karst cavities and hydraulic replenishment but also affected by the composition of filler in karst cavities.Seepage erosion takes away the filler with water flowing，and the catastrophic water inrush ensues.Moreover，water inrush is characterized by its concealment and suddenness.This paper aims to reveal the catastrophic mechanisms and early warning indicators of seepage erosion -type water inrush in karst cavities.［Methods］ This paper used the smooth particle hydrodynamics method to systematically study the catastrophic evolution of seepage erosion -type water inrush in karst cavities considering the particle gradation of filler，confining pressure stress，and flow velocity.This study reveals that the sudden change in particle loss rate can be used as a characteristic signal for catastrophic water inrush.By analyzing the patterns among the particle gradation，confining pressure stress，flow velocity，and particle loss during the change，the particle loss rate during the sudden change under different influencing factors is also examined，and the early warning indicators for the seepage erosion -type water inrush in karst cavities are determined.［Findings］ When the content of fine particles such as rock debris and fine sand is greater than 60%，the sudden change point of the particle loss rate corresponds to a flow velocity of 1.6 m/s and a confining pressure stress of 2.6 MPa，and the warning range of the particle loss rate is from 8% to 24%.When the content of coarse particles such as coarse sand and gravel exceeds 40%，the flow velocity at which the particle loss rate undergoes a sudden change is 3.0 m/s；the confining pressure stress is 4.5 MPa，and the warning value of the particle loss rate is from 8% to 45%.By comparing the critical sudden change points of the seepage erosion -type water inrush based on the indicators of particle loss rate and flow velocity，it can be observed that the sudden change point of the particle loss rate occurs earlier than that of the flow velocity.Using the particle loss rate as the early warning indicator will be more effective than the traditional indicator （flow velocity ）.［Conclusions ］ The gradual increase in the permeability of the karst cavity is a process that evolves from a slow quantitative change to a sudden change.Using the particle loss rate as the criterion for identifying the seepage erosion -type water inrush is more in line with the physical occurrence mechanism of this disaster.