In recent years, voltage instability has focused on many of its power system users, as well as the growth of demand for electricity and the economy and the environment, has led to the expansion of new energy use. The purpose of this paper was to use a new method for determining the optimal alternative and the minimum number of PMU units in the network based on the best PSO algorithm. From the perspective of the PMUs in the system, location optimization is performed based on the mode of estimation for variable voltage and control variables in a distribution network with DG resources and multiple loads. The purpose of this research is to determine the optimal alternative and the minimum number of units of the PMU and the difference in voltage voltages in the network based on the algorithm.