This paper describes optimal sizing of FACTS devices based on Particle Swarm Optimization for minimization of transmission loss considering voltage profile and cost function. Particle Swarm Optimization (PSO) is one of the artificial intelligent search approaches which have the potential in solving such a problem. In this study one of FACTS devices is used as a scheme for transmission loss. For this study, static var compensator (SVC) is chosen as the compensation device. The effect of population size during the optimization process towards achieving the solution is also investigated. Validation through the implementation on the IEEE 30-bus RTS indicated that PSO is feasible to achieve the task.