Abstract: This paper establish finite element model of explosion-proof manned vehicle , combined with driving cycle of explosion-proof manned vehicle, make statics analysis and modal analysis for body of explosion-proof manned vehicle. Sensitivity analysis of body structure provides the necessary data for body lightweight designing.On the basis of sensitivity analysis, determine the light body mass as the objective function, the thickness of the body parts as design variables, body torsional stiffness is less than required value as constraint conditions, to make the lightweight optimization design of car body, after the lightweight optimization design, body has reduced weight by 8.83%, and has achieved expected effect.