The invention relates to the technical field of heat treatment, and discloses an excavator boom shape-righting stress-eliminating system and a method for shape-righting stress-eliminating, wherein the shape-righting stress-eliminating system comprises an annealing furnace, a working platform, a first positioning pin for limiting a boom cylinder hinge hole position of a boom, a second positioning pin for limiting a position of a bucket rod connecting hinge hole after the shape-righting, a third positioning pin for limiting the position of a rotary table connecting hinge hole after the shape-righting, a first press block with gravity centre acting on a central line of the bucket rod connecting hinge hole of the boom, a second press block with gravity centre acting on the central line of the rotary table connecting hinge hole of the boom, and a support element for supporting steel casting opening part of the front support of the boom, wherein a heat insulating layer of the working platform is matched with the furnace wall of the annealing furnace hearth to form a sealed hearth. The shape-righting stress-eliminating system and method of the excavator boom can well eliminate welding stress and right shape of the boom simultaneously, and the treatment process after the boom is welded is simplified.