Abstract: Taking underground mine stope as the object of study, a fill-rock seepage model was established and the seepage pres-sure and flow formula of water in backfill-rock were deduced according to the practical situation which confirmed the initial and boundary conditions. Based on that, the seepage laws and influencing factors were analyzed. The results show that in backfill, the flow increases rapidly in the initial stage, then reaches a peak and gradually declines; the seepage pressure decreases gradually and tends to be stable;the larger the permeability, the larger the flow and pressure drop;the higher the height, the smaller the flow and the larger the pressure drop;the smaller the porosity, the higher the pressure. Porosity has different effects on the flow in different stages. In the rock, seepage pressure has no relationship with the permeability but greatly affected by the seepage of back-fill and declines with time. The flow only relates to the rock mass permeability.