Abstract: The usage of the seatbelt as a part of the vehicle protection system has immensely promoted occupant safety.However, recent accident investigation shows that it is necessary to increase the chest injury protective efficiency in frontal impact condition.This study aims to investigate the influence of seatbelt system design variables on occupant chest injury related physical parameters at varying impact conditions, especially concerning with the chest deflection and distribution of rib stress/strain.The study is conducted by using human body FE model in combination with post mortem human subjects tests.An FE model of the belted occupant is therefore established by using a baseline human body FE model (GHBMC), which is validated according to detailed experimental data regarding kinematics, seatbelt force and chest deflection.A parameter study is implemented in terms of seatbelt position, seatbelt angle and impact speed to determine the influence of seatbelt utilization on occupant thoracic injury in frontal impact.The results show that the influence of seatbelt position on chest deflection and distribution of rib stress/strain is greater than that of the seatbelt angle.Meanwhile, the trends of chest deflections are the same with the trends of the rib stress/strain responses while the changes of seatbelt design variables.This study provides a virtual test method on investigation of the chest injury biomechanics related to the seatbelt design variables.Furthermore, the results from this study of chest injury mechanism will also provide a reference for optimizing of the occupant restraint system.