Underwater rubble mound foundation is widely applied in coastal engineering,and heavy hammer tamping is one of the main method for the rubble mound foundation.This paper aimed at that the tamping energy can’t be determined due to the influence of the water resistance during the construction of the dynamic compaction in water.Experimental study on the motion characteristics of the cone-like pounder is made by the method combining the theoretical calculation,model test and numerical simulation.The numerical computation method to determine the drag force coefficients is obtained,which provides the basis for calculating the tamping energy of different shapes of pounder.