Computational human body models, especially detailed finite element models are suitable for investigation of human body kinematic responses and injury mechanism. A real-world lateral vehicle-tree impact accident was reconstructed by using finite element method according to the accident description in the CIREN database. At first, a baseline vehicle FE model was modified and validated according to the NCAP lateral impact test. The interaction between the car and the tree in the accident was simulated using LS-Dyna software. Parameters that affect the simulation results, such as the initial pre-crash speed, impact direction, and the initial impact location on the vehicle, were analyzed. The parameters were determined by matching the simulated vehicle body deformations and kinematics to the accident reports. The output speed and acceleration of rear seat from the vehicle-tree simulation will be directly applied to a simplified occupant-seat system using the CHARM-10 model to simulate the occupant-vehicle interaction in the next study. These results have shown that FE simulation can help in accident reconstruction and investigation of the pediatric injury in real-world impact accidents.