The invention belongs to the technical field of coal chemical engineering, and relates to a steam self-feeding method of a system for producing synthetic ammonia through a pulverized coal pressure gasification technology. Water gas led out from a gasifying furnace is filtered, the filtered water gas enters a boiler I, and high pressure steam is produced as a byproduct in the boiler I; the water gas led out from a gasification work section sequentially enters a converter furnace and a boiler II in a conversion work section, and high pressure steam is produced as a byproduct in the boiler II; the water gas led out from the conversion work section goes through a purifying work section, and then sequentially enters a synthesis tower and a boiler III in a synthesis work section, and high pressure steam is produced as a byproduct in the boiler III; and the high pressure steams produced in the boiler I, the boiler II and the boiler III are overheated by a superheater, and the overheated steam is used as steam needed by steam turbine driving in the system in order to realize steam self-feeding. The method has the advantages of simple route, less device investment, increase of the utilization efficiency of high-grade heat, reduction of the energy consumption of the system, and alleviation of the pollution to the environment.