The invention relates to a discharging method of rectangular parts cut on a rectangular raw material, and aims at providing an excess-material-centralizing-oriented rectangular part optimizing discharging method. The method comprises the following steps that 1, a raw material basic information set (M, L, W, S) and a rectangular part basic information set (n, l, w, do) are initialized, and the current part need number d is made to be equal to do; 2, the raw material basic information set (M, L, W, S) is traversed, and a temporary stock layout (j, Ij, Fj, s) is screened out for each raw material based on a stock layout batten optimizing rule; 3, the raw material utilization rate of each temporary stock layout is calculated, the temporary stock layout with the maximum raw material utilization rate is selected out to serve as a preferred stock layout (j, I, F, s), and the remaining part need number dr is calculated to be equal to d-Fl; 4, whether the remaining part need number dr is 0 or not is judged, and if not, d is made to be equal to dr, the step 2 is executed till dr is equal to 0, and therefore a discharging scheme which is composed of the preferred stock layout (j, I, F, s) and meets the target need number do is obtained. On the premise of guaranteeing the high raw material utilization rate, centralizing of excess materials on the raw materials is achieved, and the rectangular part discharging cutting process is simplified.