Abstract: The seepage characteristics of sand and soil can be well described by Darcy's law.But to rock, this is very complicated because the cracks exist in it.The statistic theory of cracks put forward by Dienes successfully expounded the seepage phenomena observed in rocks.On the basis, this paper setup a new seepage model.Three parameters were considered in this new model, i.e, the average rate of fluid through every crack, the number density of cracks in per unit volume and the extent of cracks'penetrance.Base on the stochastic theory and hydrodynamics theory of fluid through a single crack, integral formulas of permeability were set up and their forms were consistent with Darcy's law in inhomogeneous media.