The mean energy flux of progressive gravity waves of finite amplitude in water of arbitrary uniform depth is accurately partitioned by a relative simple method. It is comfirmed by calculation of the mean energy flux that the energy flux is chiefly due to the work done by the pressure forces of fluid. However, sometimes the energy fluxes caused by the kinetic energy and potential energy also possess fair percentage, and in the extreme case they may reach about 30% of the total energy flux. In this paper the error due to the commonly used small-amplitude theory being applied to the calculation of the energy flux is discussed in detail. In addition, the method of the energy flux partition is applicable to the cases of both finite and infinite water depth, and it is far more simple and direct than the method used by Starr and Platzman. The mean energy flux of progressive gravity waves of finite amplitude in water of arbitrary uniform depth is accurately partitioned by a relative simple method. It is comfirmed by calculation of the mean energy flux that the energy flux is chiefly due to the work done by the pressure forces of fluid. However, sometimes the energy fluxes caused by the kinetic energy and potential energy also has fair percentage, and in the extreme case they may reach about 30% of the total energy flux. In this paper the error due to the commonly used small-amplitude theory being applied to the calculation of the energy flux is discussed in detail. In addition, the method of the energy flux partition is applicable to the cases of both finite and infinite water depth, and it is far more simple and direct than the method used by Starr and Platzman.