The invention provides a gas atomization and decarburization steelmaking method of high-temperature molten iron. A high-temperature atomization chamber of an atomization furnace is filled with high-pressure oxide gas in a specified temperature range. By a gas atomization technology, high-temperature molten iron with high carbon content is broken into superfine iron drops within specified atomization time, and under self kinetic energy and gravity action, the superfine iron drops fall and fly in a high-pressure oxide gas environment and are condensed, forming iron powder; in atomization and flying processes, carbon in the iron drops and/or the iron powder has chemical reaction with the oxide gas, forming CO or CO2 gas; and the cooled iron powder is converted to steel powder and falls in a collector at the lower part of the atomization furnace. By adopting the high-pressure and high-temperature oxide gas atomization chamber, the liquid drops are kept for certain time, and the rapid conduction of the decarburization of the liquid drops and the environmental gas is promoted; the shape of the atomized powder depends on the surface tension of molten metal and cooling and crystallizing time after the molten metal is broken, the gas atomization and cooling time of the high-temperature molten iron is long, the powder body easily forms corners, and the compressibility of the powder is great; and the production efficiency of preparing the steel powder by the molten iron is increased.