Abstract: This paper presents the voltage generating process of synchronous generator. The aim of this paper is to understand the excitation system of synchronous generator. A direct current(DC) is applied to the rotor winding of a synchronous generator to the produce the rotor magnetic field. A prime mover rotates the generator rotor to rotate the magnetic field in the machine. A three phase set of voltages is induced in the stator winding by the rotating magnetic field. Excitation is the important part of synchronous generator. Synchronous generator excitation system consists of exciter, automatic voltage regulator, rectifier, step down transformer. The basic function of an excitation system is to provide direct current to the synchronous generator field winding. Voltage generating process simulate the MATLAB software.