Abstract: In order to study the mechanism of water-sand inrush disaster Caused by the mining-induced crushed rock mass in shallow coal seam in western mining area,based on the two phase flow theory,the paper analyzed the characteristics of two phase water-sand flow in crushed rock mass and the suitable theoretical model,put forward the basic seepage parameters for two phase water-sand flow in crushed rock mass,researched the extraction method for the seepage parameters and the change rule of seepage parameters in different particle size.The research results indicate that the two phase flow continuum model is fittingly employed to analyze the two phase water-sand flow in crushed rock mass,which belongs to the non-Darcy seepage and non-Newton fluid；the basic characteristic parameters in two phase water-sand flow contain fluidity,non-Darcy β factor,and acceleration coefficient ca；combined with the numerical analysis,the basic parameters in two phase water-sand flow are effectively extracted,on the basis of sand phase pressure gradient time series and seepage velocity time series；as the increase of particle size of crushed rock mass,the non-Darcy β factor and acceleration coefficient decrease,while the fluidity augments.