Abstract: Based on the secondary development of CATIA software and VBA language programming, the key parameters in the 3D data of side door system are automatically collected and the parameter preset for preliminary design is completed. According to the structure and movement features of side door system, a spatial geometric model for side door closing energy and mathematical models for fluid mechanics and dynamics are established. Through the secondary development of Excel platform and VBA language programming, the above-mentioned geometric model and calculation model are gathered into an Excel file with a man-machine interactive operation interface designed. Through one-click calculation, the designed preset parameters of different vehicles are input, and the corresponding minimum closing energy for the site door system is calculated. The comparison between calculated and measured data shows that their conformation rates are all over 80%, verifying the accuracy of the calculation program for closing energy in the forward design of side door

Key words: side door system, closing energy, forward design, secondary development, VBA programming