Method for smelting ultra-low carbon steel

The invention provides a method for melting ultra-low carbon steel. The method adopts a desulfuration of molten iron-converter-RH-continuous casting process, wherein a sulfur content in the molten iron is 0.002%-0.006% after desulphurization; converter smelting controls oxygen blowing time, an oxygen gun flow, a bottom-blowing intensity and a smelting period, adopts slag-stopping tapping, steel tapping with a content of C being 0.06%-0.08% and with a temperature of 1650-1680 DEG C, and an oxygen content in the molten iron is 0.03%-0.05%; an RH adopts forced decarburization with a highest vacuum degree of 67-100 MPa and decarburization time of 15-27 min, and a carbon content in the molten iron is 0.0010%-0.0020% and a dissolved oxygen content in the molten iron is 0.025%-0.040% after the decarburization; the molten iron is recycled for 3-5 min after deoxidation by adding aluminium and recycled for another 3-5 min after adding other alloys; a nitrogen content in the molten iron is 0.0015%-0.0035%, and the temperature is 1590-1640 DEG C; and killed steel treatment is carried out for 10-30 min. The method adopts converter tapping with a high carbon and low oxygen content, can use less or not use slag modified agents during the tapping process, accelerates the production rhythm, makes the molten steel cleaner, and reduces the production cost.