The invention belongs to the field of forging, in particular to a design method for 9Ni large forge piece construction forming. The design method is suitable for large-section forge piece forming andimproving quality reliability of a large force piece and is used for solving the problems of center hole shrinkage, loosening and other problems hard to control in a traditional large forge piece manufacturing technology. The design method comprises the technologies of smelting, continuous casting blank surface washing and milling, vacuum packaging, high-temperature heating, high-pressure forgingand welding, forging and forming and the like. The metal traceless construction thought is adopted, a plurality of pieces of homogenized base metal are subjected to large deformation at the high temperature after being subjected to surface cleaning and vacuum packaging, metal solid connection is achieved, and an interface is sufficiently closed up. The core thought is breaking the whole into partsand making large from small, the large component homogenizing preparing technology is changed, the component breaking limit is broken through, and the quality reliability of a large forge piece is enhanced.