Aeronautical monolithic components are characteristic of thin wall, large size, high machining accuracy, many material removals, and so on. The pre-stretched aluminum alloy thick plates are usually selected as blanks of aeronautical monolithic components. In the following process of high speed machining, the residual stresses will release from the blanks with the removal of material. In sequence, a new equilibrium of residual stresses can be achieved by the workpiece deformations which can strongly impact the machining quality. Therefore, the effect of residual stress release on machining deformation is investigated to control the machining quality. It is very crucial for the realization of machining process with high efficiency and precise. Above all, according to separation of a blank into removed materials and formed workpiece, the initial residual stresses can be divided into released stresses and efficient stresses so that the analysis model of machining deformations is deduced by the static equilibrium conditions and bend deformation theory. And then, finite element method is employed to solve the analysis model of machining deformations. The experiment of machined workpieces, carried out in NC machining factory, shows that both the amplitude and deformation curve, the simulated results are good agreement with the measured data. However, the measurement error of residual stresses causes 10% difference of the amplitude of the simulated results with the experimental values. Finally, an optimal model with the objective of minimum machining deformation is formulated to find the proper machining position. Therefore, a crossover iterative method is next suggested for the proposed optimal model. The initial machining position is selected from the minimum value with a given step along the positive direction. According to the sign difference of machining deformations at the current position with the last one, the step and its direction can be determined for the next selection. If the sign of the current deformation is same as the previous deformation, the step and its direction for the next position is same as the current position. Otherwise, it is chosen with the decrease step along the negative direction. The search procedure for the machining position is exceeded until the absolute value of the current step is within the given threshold value. In comparison with middle position method which is usually adopted by the enterprises, the presented crossover iterative method can decrease 99.79% machining deformations.