Many thermal processes have been developed in order to eliminate the municipal solid wastes or produce energy from them. These processes include a wide range of applications from the simplest burning system to plasma gasification. Plasma gasification is based on re-forming of molecules after all molecules convert to smaller molecules or atoms at high temperatures. In this work, the production of fuel gas is aimed by plasma gasification of municipal solid wastes in high temperatures. Because of this, a plasma reactor of the capacity of 10 kg h(-1)was designed which can gasify municipal solid wastes. Plasma gasification with and without steam and oxygen was performed in temperatures of 600, 800, 1000, 1200, 1400 and 1600 degrees C in the reactor. A gas mixture containing methane, ethane, hydrogen, carbon dioxide and monoxide, whose content varies with temperature, was obtained. It was found that plasma gasification (or plasma pyrolysis, PG), plasma gasification with oxygen (PGO) and plasma gasification with steam (PGS) were more prone to CO formation. A gas product which was consisted of 95% CO between 1200 and 1400 degrees C was produced. It was observed that a gas with high energy capacity may be produced by feeding oxygen and steam into the entrance of the high temperature region of the reactor.