The invention discloses a supercritical water gasification-oxidation method for treating organic wastewater and recycling synthesis gas. The supercritical water gasification-oxidation method comprises the following steps that: (1) the organic wastewater enters a preheater and a supercritical water gasification device sequentially by a high-pressure pump, and oxygen is divided by a compressor, so that one part of oxygen enters the supercritical water gasification device; (2) fluid from an outlet of the supercritical water gasification device enters a high-pressure gas-liquid separator by a heat exchanger, the synthesis gas of H2, CO and CH4 on the upper part is recycled, the fluid at the bottom enters a heater and a supercritical water oxidation reactor sequentially, and the part of oxygen which is divided by the compressor enters the supercritical water oxidation reactor; and (3) the fluid passing through the supercritical water oxidation reactor passes through a cooler and a back pressure valve sequentially and is discharged under the condition of reaching the standard. The supercritical water gasification-oxidation method can be widely applied to the treatment of the high-concentration organic wastewater.