A constructing-and-forging method for preparing homogenized forged pieces, wherein: firstly, preparing preformed billets: cutting off a plurality of continuous casting billets to have certain sizes, milling and smoothing surfaces of the billets to be welded by a milling planer, performing vacuum plasma cleaning operation to the surfaces to be welded, stacking the plurality of billets and sealing around the surfaces to be welded in a vacuum chamber by electron beam welding; then forge-welding and homogenizing the preformed billets: heating the preformed billets to a certain temperature in a heating furnace and taking the heated preformed billets out of the heating furnace, forging the preformed billets by a hydraulic press, using pressure dwelling and temperature dwelling means during a first upsetting process to weld the surfaces completely together, then using three-dimensional forging to disperse the welded surfaces such that composition, structure and inclusion of the interface areas are substantially same as those of the bodies of the billets; final forming: forging the preformed billets to have final shape and size; wherein the method comprises: a first step, cutting off the plurality of the continuous casting billets according to a certain specification; a second step, machining and cleaning the surfaces of the billets to be welded; a third step, welding the billets by vacuum electron beam welding to seal the billets; a fourth step, heating the billets before forging; a fifth step, upsetting and forge-welding the billets using a pressure dwelling and forge welding method; a sixth step, diffusion bonding the billets under a high temperature; a seventh step, stretching the billets in the Y direction; an eighth step, stretching the billets in the X direction; a ninth step, stretching the billets in the Z direction; and a tenth step, forging the billets to have final shape and size. firstly, preparing preformed billets: cutting off a plurality of continuous casting billets to have certain sizes, milling and smoothing surfaces of the billets to be welded by a milling planer, performing vacuum plasma cleaning operation to the surfaces to be welded, stacking the plurality of billets and sealing around the surfaces to be welded in a vacuum chamber by electron beam welding; then forge-welding and homogenizing the preformed billets: heating the preformed billets to a certain temperature in a heating furnace and taking the heated preformed billets out of the heating furnace, forging the preformed billets by a hydraulic press, using pressure dwelling and temperature dwelling means during a first upsetting process to weld the surfaces completely together, then using three-dimensional forging to disperse the welded surfaces such that composition, structure and inclusion of the interface areas are substantially same as those of the bodies of the billets; final forming: forging the preformed billets to have final shape and size; wherein the method comprises: a first step, cutting off the plurality of the continuous casting billets according to a certain specification; a second step, machining and cleaning the surfaces of the billets to be welded; a third step, welding the billets by vacuum electron beam welding to seal the billets; a fourth step, heating the billets before forging; a fifth step, upsetting and forge-welding the billets using a pressure dwelling and forge welding method; a sixth step, diffusion bonding the billets under a high temperature; a seventh step, stretching the billets in the Y direction; an eighth step, stretching the billets in the X direction; a ninth step, stretching the billets in the Z direction; and a tenth step, forging the billets to have final shape and size. a first step, cutting off the plurality of the continuous casting billets according to a certain specification; a second step, machining and cleaning the surfaces of the billets to be welded; a third step, welding the billets by vacuum electron beam welding to seal the billets; a fourth step, heating the billets before forging; a fifth step, upsetting and forge-welding the billets using a pressure dwelling and forge welding method; a sixth step, diffusion bonding the billets under a high temperature; a seventh step, stretching the billets in the Y direction; an eighth step, stretching the billets in the X direction; a ninth step, stretching the billets in the Z direction; and a tenth step, forging the billets to have final shape and size.