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.).Products conversion is obtained in a device by electric discharge plasma GlidArc-I, installed in a superior compartment of the device and communicating directly with its full lower compartment by a refractory porous containing oxides of nickel. The GlidArc-I first of all serves to light the electro-reinforced total combustion of a flux reduce a carbonaceous (fuel) mixed with a gas combustive base of oxygen (for example air). This combustion warms the then catalytic refractory of post-plasma until a favourable temperature is obtain to the partial catalytic oxidization of fuel toward the syngas or the mixed syngas with methane and the ethylene (reformats). Finally, these discharges maintain and consolidate this partial oxidization without production of soot and with a total conversion of fuel. The power dissipated in the GlidArc-I is negligible (2% to the maximum) in relation to the power thermal lower reach by the flux of the syngas or of reformats it thus products.