Abstract: In this Study changes of uncontinuous potential functions at the interface wereused to simulate the immiscible displacement in porous media. The elliptic partialdifferential equation was changed to a seven-pomt molecule form algebraic equation inthree dimensions using the finite difference method. The Strongly implicit procedurewas adopted to determine the potential functions at every time instant. Then thechange of interface was determmed. The simulation was continued until thedisplacement changed to unstable state. The effect of capillary pressure, wettingproperly, and nonuniformity of permeability were consthered.