The load duration curves of power distribution networks are necessary data for optimal operating, planning and designing electric power networks. It is essential for the problems which require the energy loss calculations, such as reactive power compensation or economical comparison of designed networks... Normally due to the lack of load duration curves data, these problems are solved by using approximately hour-loss coefficient. This paper presents an approach for establishing the load duration curves, based on the collective data from consumed energy of participated loads in Vietnam electric power distribution networks. The results allow determination of power-consumed characteristics in different distribution networks of Vietnam, as well as calculation of the equivalent hour-loss coefficients.