Abstract: Semi-solid forming process of an impeller was simulated with DEFORM3D.The changing pattern of process parameters was obtained.It is indicates that the impeller can be forged by the method of semi-solid extrusion-forging and the deforming process can be divided into 3 stages.The forming of blades is depending on the extrusion of materials.During the forming,uneven deformation is existed in the billet,especially in the field of blade root.The forging load is increased rapidly during the later stage.The maximum forging load is about 2 780 kN.