Springback is one of the main factors affecting the NC singlepoint progressive forming of sheet metal. In order to analyze the influences of process parameters on the singlepoint progressive forming of metal sheet, the springback experiments for forming angle of square box produced by aluminum plate were conducted by the CNC milling machine. Then, the forming angle after springback was measured by angle ruler, and the influence of each process parameter was measured by change rate of forming angle and springback angle. The process parameters in experiment include forming angle, feeding speeds in the X and Y directions, feeding speed in Z direction, and feeding displacement in the Z direction. The results show that the larger the forming angle is, the smaller the change rate of forming angle and the springback angle are; the larger the feeding speeds in the X and Y directions are, the larger the change rate of forming angle and springback angle are, and the smaller the feeding displacement in the Z direction is, the smaller the change rate of forming angle and springback angle are. However, the feeding speed in the Z direction has no significant effect on the springback.