In order to reduce the pre-processing cost for simulating multiple assembly sequences, an input file generation module is proposed for the welding distortion simulation by ABAQUS. This module is based on the input file information of an assembly sequence and considers contact relation between parts and weld lines in the assembly. The proposed module is applied to assembly structures and the results show that it is useful to reduce the pre-processing cost for the welding distortion simulation with regard to the different assembly sequences.