Nowadays, voltage sag has become one of the most concerned about power quality problems, accurately locate the position of the voltage sag is a sufficient condition to ensure the stability of power system operation and the process of electricity market. Distributed generations (DG) are widely connected in the distribution network has changed the direction of the load flow and the operation mode of the distribution networks, several existing location method has not met accurately locate the voltage sag of grid with DG. According to location of voltage drop of distribution network with DG, This paper which based on the distribution network fault location method feeder terminal unit ,presents a method which use preliminary improved adaptive matrix method to determine the fault zone where the voltage sag, and then through the use of improved impedance method accurate locate the location of source of voltage sag . The advantages of the method of the matrix method combining with impedance method in a small amount of calculation and with good accuracy of are verified by results of calculation example and simulation.