The invention discloses a production method for ultralow-oxygen-content molten steel of ultralow-low-carbon steel, and belongs to the technical field of steel making. The technological route comprises molten iron pretreatment, converter smelting, RH vacuum refining and slab continuous casting. Molten iron pretreatment employs KR method for desulphurization; converter smelting is used for controlling endpoint carbon content and endpoint oxygen content; steel tapping is performed during a boiling state of a converter, slag-stopping operation is performed during steel tapping, and lime and fluorite are added for adjusting the slag; and during RH vacuum refining, the highest vacuum degree is controlled, after decarburization is finished, Al is used for deoxygenation, also a deoxidizer is uniformly spread on the slag surface and stirring is performed, so that ladle slag is subjected to deoxygenation, and then high-vacuum-degree circular processing is guaranteed for 5 min or more. The method is capable of effectively removing free oxygen in molten steel and stably controlling the T.O content of the molten steel during RH tapping to be 15 ppm or less.