The crashworthiness topology optimization of body in white (BIW) under frontal impact loading was carried out by using the equivalent static loads method (ESL). Inertia relief was introduced as boundary conditions; strain energy was adopted as strain energy and relative displacement was employed as the compliance index of the components and parts. A series of comparative studies were executed to discuss the effects of different boundary conditions and various optimization objectives. The results show that if an inertia relief is used as a boundary condition, the ESLbased topology optimization results have a tendency to distribute more material on the impact occurred position, while the single point constraint (SPC) boundary conditions tend to concentrate more materials on the contrived SPC restrained positions. In addition, minimizing relative displacements is suitable for the ESLbased topology optimization, but maximizing relative displacements should be transformed into constraints to perform the optimization.