Abstract: Optimum design of complex flanging trimming line was studied. An iterative method based on errorcorrection was proposed. Based on finite element method (FEM) simulation of LSDYNA, the blank was corrected according to the error values of simulation results and the target curve. After one or two iterations, an exact trimming line was obtained. The program could automatically call LSDYNA solver, which greatly increased the efficiency of the trimming line optimization. A flanging simulation study proved that the method was effective.