A seat frame structure in automotive vehicles made of polymer matrix composite(PMC) with reinforced by X-shape steel frame was developed to obtain weight reduction at low cost. The frame structure was designed and analysed using finite element analysis(FEA) and was compared with experimental impact test to verify the structural safety after fabricated. The design model based on safety was analysed with appropriate boundary conditions and loading conditions. Each result was utilized to modify the actual shape to obtain a lighter, safer and stabler design. It was found that the substitution of PMC material reinforced by an X-shaped steel frame resulted in a weight reduction effect with equivalent strength, impact characteristics and fracture property.