The invention discloses a manufacturing method of an IF (Interstitial-Free) steel tundish, and belongs to the technical field of ferrous metallurgical continuous casting tundish processes. The manufacturing method of the IF steel tundish comprises the following steps: (1) three-dimensional modeling: drawing a three-dimensional geometric model of a deflector hole by using three-dimensional modeling software; (2) 3D printing: inputting the three-dimensional geometric model of the deflector hole into a 3D printing machine for 3D printing of an elbow made of an ABS material, the elbow being matched with the structure size of the defelctor hole; (3) installation of the elbow: burying the elbow into a heightened layer in an IF steel tundish building process; (4) installation of a residue-blocking dam: installing the residue-blocking dam into a tundish body; and (5) forming of the deflector hole: baking the IF steel tundish, wherein the elbow made of the ABS material is combusted under heating and disappears in the baking process, so that the deflector hole with a satisfactory structure size is formed in the heightened layer. The manufacturing method is suitable for producing IF steel and can obviously reduce the molten steel injection amount.