NOVELTY - The horizontal fixed bed catalytic reaction system comprises: an input reactant injecting device for injecting a mixture of lignocellulosic biomass received from bio-oil and water as a reactant; a pre-heating device for pre-heating the reactant; a horizontal reaction apparatus for performing a catalytic reaction on the preheated reactant in a supercritical water condition to produce a synthesis gas; and post-processing unit for removing a foreign substance in the produced synthetic gas. The injecting device comprises a water storage tank, a cylindrical input device, and a high pressure pump.    USE - The horizontal fixed bed catalytic reaction system is useful for continuously reforming bio-oil in a supercritical water condition (claimed).    ADVANTAGE - The horizontal fixed bed catalytic reaction system is capable of economically and continuously reforming the bio-oil.    DETAILED DESCRIPTION - The horizontal fixed bed catalytic reaction system comprises: an input reactant injecting device for injecting a mixture of lignocellulosic biomass received from bio-oil and water as a reactant; a pre-heating device for pre-heating the reactant; a horizontal reaction apparatus for performing a catalytic reaction on the preheated reactant in a supercritical water condition to produce a synthesis gas; and post-processing unit for removing a foreign substance in the produced synthetic gas. The reactant injecting device comprises a water storage tank installed in a lower part, a cylindrical input device, and a high pressure pump. The cylindrical input device comprises a cylindrical body. Air outlets are installed at the cylindrical input device. On-off valves are arranged in the air outlets. A piston pressurizes a cylinder inner space connected with a reactant chamber and a water chamber. The pre-heating device comprises a preheater, a flaw installed at backward and forward ends of the preheater, a thermocouple that is arranged inside the preheater and measures a temperature of the reactant, an inner heater that is arranged inside the preheater and heats the reactant, and an outside heater that heats the reactant and is installed at a outer side surface of the preheater. The horizontal reaction apparatus comprises a thermocouple that measures an inner temperature of the horizontal reaction apparatus, and a horizontal reactor unit in which an inner portion is charged with catalyst. A gas flow rate measuring device measures a flow rate of gas. A post pressure controller decompresses the pressure of a product. A flash chamber separates a depressurized product. A filter filters the solid material from the product at an ambient pressure. A heat exchanger exchanges the reaction heat produced in the horizontal reaction apparatus. An INDEPENDENT CLAIM is included for a method for continuously reforming bio-oil in a supercritical water condition.