In this paper, we use SVC and TCSC simultaneous controllers in order to increase the stability of four-machine power system. Today, development of power electronic technology has made us to apply the stabilization feature of Flexible AC Transmission Systems (FACTS) devices to control the power system oscillations. Thyristor Controlled Series Capacitor (TCSC) and Static Var Compensator (SVC) are the examples of the FACTS devices and their synthesis are used in this paper to increase stability of the power system. Then the parameters of the system are optimized by Adaptive Neuro-Fuzzy Inference System (ANFIS) model and therefore, the stability of the system improve. In this paper the results of simulation with MTLAB software are done. Analysis of the simulation results shows that the proposed controllers can improve successfully stability of the power system and therefore, the transmission power increases.