This book presents a novel method for optimal location of FACTS controllers in a multi machine power systems and also give the solution with each of the FACTS device. Using this proposed method, the location of FACTS controller, their type and rated values are analyzed and optimized simultaneously.With the aid of FACTS technology, namely Static Var Compensator (SVC), Thyristor Switched Capacitor Variable Reactor (TCVR) and Unified Power Flow Controller (UPFC) etc., the bus voltages, line impedances and phase angles in the power system can be controlled quickly and flexibly. In my paper IEEE standard 14 & 30 bus systems were taken for obtaining optimum solution.Simulation results shown that the obtained output is feasible and most accurate solution in the OPF solution. FACTS devices can direct the active and reactive power control and flexible to voltage-magnitude control simultaneously, because of their adaptability and fast control characteristics.