In order to assure the accuracy of trimming springback of multi-step forming by finite element method, a trimming algorithm based on self-adaptive template of trimmed elements was proposed. In this algorithm, the intersection calculation between 3D trimming lines and mesh of part was executed at first. Then the accepting and rejecting judgement of elements was achieved. Finally, the method of trimming element by element along the path of the section lines was used in trimming operation. Therefore, the problems of boundary serration, axial symmetry and boundary gap have been totally avoided, and multi-trimming on refined mesh was achieved to improve the efficiency of trimming operation. The present algorithm has been integrated into the independently developed KMAS forming analysis system. By using the numerical simulation on automotive underbody cross member which was provided by benchmark test of NUMISHEET 2005, the applicability and reliability of introduced algorithm were verified.