Abstract: A parametric model was established with SFE-CONCEPT software for a BIW (body in white). Firstly, the static bending-torsion stiff and the lower-order modal of BIW were simulated based on finite element method, and the results were compared with tests. Then connecting the parametric BIW with power train and chassis, the crash safety performances were simulated based on finite element method and compared with tests. The comparison results between simulation and test validate the parametric model of BIW. Secondly, the lightweight and safety of BIW structure were optimized. Due to the safety simulation analysis belongs to non-linear analysis, the optimization process can't fully achieve automatic, needing manual intervention to extract safety performances in tradition way. In order to achieve the optimization process automation, a batch file was compiled to extract safety performances. The lightweight optimization results show that, the bending stiff can increase 0.15%, the torsion stiff can reduce 0.03%, torsion modal frequency can increase 1.30%, bending modal frequency increased 0.09%. And under the condition that the crash safety performances keep no changing, the weight of lightweight optimization BIW can reduce 24.17 kg, the reduction rate reaches 7.63%. The multi-objective collaborative optimization can provide obvious lightweight effect for BIW.