High-strength steel, which has higher strength than ordinary steel, has emerged as a representative lightweight material because of its superior price competitiveness and easy application of manufacturing processes compared to other lightweight materials such as nonferrous metals and sandwich plates. Thus, the purpose of this study was to reduce the thickness and light weight of parts by applying high strength steel more than 600 MPa to various body parts. TR590 and DP590 high tensile steels were applied to the reinforcement seat belt front top and bottom components respectively. To this end, the impact simulation was performed, and the safety of the parts was investigated through FE-Analysis. Prototype molding evaluation confirmed the possibility of mass production of reinforcement seat belt front upper and lower components, using high tensile steel.