The invention discloses a smelting method for ultra-low carbon steel. The smelting method for the ultra-low carbon steel comprises the steps that molten iron is smelted through a converter; when steel is discharged out of the converter, high-calcium aluminum slag balls are added according to the end-point oxygen content of the converter so as to reduce the TFe content in top slag, so that molten steel is obtained; the molten steel is subjected to RH vacuum refining, the high-calcium aluminum slag balls are scattered to the slag surface evenly when RH vacuum breaking is completed, and the TFe content in the slag is further reduced, so that molten steel with a high clean degree is obtained; and a finished product is obtained by continuously casting the molten steel with the high clean degree. By means of the smelting method for the ultra-low carbon steel, the oxidability of ladle slag of the ultra-low carbon steel can be reduced remarkably, the castability of the molten steel is improved, and the clean degree of the molten steel is increased.