Under typical dyke conditions with cutoff wall as reinforcement measure,the seepage field is simulated numerically by theory corresponding to design standard.The seepage control efficiency and its variation laws are analyzed for cutoff wall of suspension type and semiclosure type.The factors that might affect the efficiency of cutoff wall of closure type are pointed out.The principles of design and application are discussed for cutoff wall of different types.The penetration rateexit gradient curve method is presented to design the cutoff wall of suspension type.The permeabilityexit gradient curve method,the thicknessexit gradient curve method and the B valueexit gradient curve method are presented to design the cutoff wall of semiclosure type.