Abstract: When the mining-induced fracture zone develops to the loose aquifer, it will cause the inflow of water and sand mixture, which may lead to water and sand inrush. On the basis of considering water pressure and drag force, the mesomechanics model of overlying loose sand layer of mining-induced fractures is established. The dynamic characteristics of fluid phase are calculated by averaging Navier-Stokes equation; with particle flow software PFC, the seepage failure of sand is studied. The results show that water pressure and fracture width have great influence on the seepage failure.