Abstract: In order to study water-inrush mechanism of collapse column and complete testing basis for water inrush of collapse column,a self-designed seepage testing system for variable mass of broken rock was used to testing the nonlinear seepage characters of variable mass of broken mudstone.The time-changed laws of losing weight, porosity,permeability, non-Darcy flow β factor of mudstone during the seepage process were researched. It shows that the seepage form of mudstone sample changed enormously during the seepage process; at the beginning of seepage,the losing weight increased rapidly,which caused the interior pore structure changing,porosity increasing and the permeability quality enhancing;the denser of the broken mudstone compressed,the larger of the losing weight was;the faster porosity of sample changed,the better of the permeability quality was;the losing weight and permeability were interacted with each other; the losing weight in the test had time-changed character,as well as permeability parameters.Finally, the process of water inrush of collapse column could be explained as follow, a large number of fine particles were lost with flow under confined ground water,which caused porosity increasing,permeability quality enhancing,and resulting in seepage great changing and water inrush.