This paper focus on the defects, such as wrinkling and warping, which generated in the process of fourroll bending for aluminum profiles with a large size Z-shaped section. A finite element analysis model for CNC four-axis roll-bending forming process of Z-shaped profile with large section was established by ABAQUS. Based on the analysis of forming defects, asymmetrical loading mode and secondary roll-bending process were presented to control forming defects. The results indicated that the secondary roll-bending could improve forming quality. Asymmetrical loading mode,the left roller was adjusted higher than the right one, which had significant inhibitory function on defects like wrinkling and warping. Experimental results proved that compared with numerical simulation results, the error was within 10%.