One of the problems responsible of power generation and transmission is the maintaining of an appropriate voltage profile by installation of reactive power supplies. In this paper, we propose a new technique for the optimal location and design of two kinds of Flexible AC Transmission System Devices (FACTS) namely: Satitic Var Compensator (SVC) and Thyristor Controlled Series Compensator (TCSC) handling the minimization of transmission losses in electrical network. Using the proposed scheme, the type, the location and the rating of FACTS devices are optimized simultaneously. The problem to solve is multi criteria under constraints related to the load flow equations, the voltages, the transformer turn ratios, the active and reactive productions and the compensation devices. Its resolution requires the employ of the advanced algorithms. Thus, we propose an approach based on the evolutionary algorithms (EA) to solve this problem multi criterion. It is about the NSGA-II method (Ellitist Non Dominated Sorting Genetic Algorithm). The Pareto front is obtained for continuous, discrete and multiple of five MVArs of compensator devices for the IEEE 57-bus test system.