The process and the device of assistance by electric discharge plasma for a partial oxidization of various liquids or gas, has for object the gas rich production of CO and H2 (syngas) can contain the CH4 and C2H4 also, this without soot formation. Carbonaceous matters considered here are fossil origin (as the diesel oil, gas, the kerosene, the naphtha, the heavy oil, the natural gas, etc.) or renewable (as the rape oil, the ethanol, the glycerol, the biooil, the molasses, the biogas, etc.).