Starting with interface effects, the motion state of the leaching solution was analyzed to find out the seepage rule in unsaturated leaching. The total suction in ore heaps is composed of the matric suction from interface effects and the osmotic suction from absorption and diffusion of the ore and solution. The inhomogeneity of medium distribution in pores and the randomness of ore shape are causes for the diversity of interface effects, which make the motion state of the leaching solution complicated. Capillary rise experiment was conducted to prove the existence of suction in ore heaps. The result reveals that the capillary rise height increases faster at the beginning of infiltration under driving force than that at the later period of infiltration. Moreover, the fitting curve reveals that the capillary rise height increases by a power function with infiltration time. Theoretical studies show that the interface effects of unsaturated seepage in leaching can be regulated by changing the physical properties of solid phase, liquid phase and gas phase.