A hot oxygen nozzle and uses thereof in a gasifier, the hot oxygen nozzle comprising an outer-ring spout, a middle-ring spout, an inner-ring spout, and a central spout all sequentially and coaxially disposed, and a cooling system; the gasifier is an entrained-flow gasifier provided with one or more nozzles on a certain plane or a plurality of planes at the top or on the periphery of the gasifier body. The nozzle has a simple structure and is easy to make and maintain. A fuel gas passage is disposed inside the nozzle. Oxygen can be heated by a combustion of fuel gas; and high-temperature and high-speed oxygen can directly ignite carbonaceous materials such as coal-water slurry and coke-oven gas. The present invention can be applied in a gasifier and then in the final process of synthesis gas preparation.