Abstract: The invention provides an electroslag fusion process for manufacturing a blade slab having a large curved surface, and it is more particularly effectively in making a blade slab which has a big width-to-thickness ratio, a large difference between the thin and the thick edges and a large curved surface. Firstly, dividing the blade slab into two or three regions according to the external shape and the sectional size of the blade slab, wherein the region which has difficulty in unilateral or bilateral mold-filling is pre-fabricated by the electroslag casting technology to produce a pre-fabricated curved slab, and then it is placed in advance in a side of an internal cavity of a mold, and then fusing the molten metal melted from a consumable electrode and one or two electroslag pre-fabricated slabs which are placed in advance in the mold by utilizing the electroslag fusion process, so as to produce the blade slab having a large curved surface.