The seepage law of leaching solution has a very important influence on the leaching rate and velocity for the dump leaching technology.The dump is consisted of ore particles,air,immobile solution and mobile solution,and ore particles are the framework of the dump.The absorb effect and surface tension on ore particles,s surface are the important factor that impel the solution flow into the dump.Under unsaturated seepage condition,relative permeability of the dump is related to the saturation.The intrinsic permeability of the fine particle area of the dump is small,the maximal limiting velocity is low,so this area becomes saturated easily.Flooding area of the dump become wider and wider with the increasing of the application rate until saturated seepage is reached in whole dump. The basic seepage equation of leaching solution is provided based on the hypothesis seepage flow instead of the true one.