The invention discloses a supercritical water oxidation reactor by using an auxiliary fuel for supplying heat, the heat required for a reaction can be supplied by using the auxiliary fuel, Material, fuel and an oxidizing agent (air or oxygen) are mixed with a high efficiency through the different directional jets for raising oxidation efficiency. According to the invention, the reactor employs a combination structure of evaporation wall and pot type backflow, the reaction vessel volume is effectively used and the reaction time is increased, the blockage problem generated by salt deposition can be also prevented, the corrosion problem of the reactor is effectively reduced. The temperature of the reactor bottom can be preciously controlled through a cooling water pipeline at the reactor bottom, thereby the safe operation of equipment is guaranteed. The reactor effectively solves the economic problem of a supercritical water reaction system by using the auxiliary fuel for supplying, the invention has the advantage of easy industrial amplification, and is widely applied to organic liquid such as high density and difficult biodegradation organic waste water/garbage leachate and the like for a harmlessness processing.