Glass fiber reinforced polypropylene (GFPP) is widely applied to automotive parts and others. Generally, the properties of the composite material increase as the content of reinforcing fibers increases. By increasing the residual fiber content of reinforced plastics, FRP can be adapted to more products. When they are adapted, the next problem is said to be a long-term physical property. However, conventional injection molding has been limited to producing short fiber reinforced polymer composites (SF-GFPP). Therefore, further improvement of mechanical properties of SF-GFPP is required. Direct fiber feed injection molding (DFFIM) was developed for long fiber reinforced polymer composites, omitting the compounding process to shorten reinforcing fibers. Reinforcing fibers are supplied to the vent barrel of the DFFIM process. Processing parameters such as matrix feed rate, fiber filling rate, injection speed and injection pressure and number of feed fibers are controlled for the desired fiber content in the composite by DFFIM. It is thought that this method affects thermal degradation of resin as well as long fiber of fiber. In this study, the mechanical properties of glass fiber reinforced PP (DFF-GFPP) prepared by using commercially available SF-GFPP and DFFIM under high temperature were investigated. Commercial products GFPP and DFF-GFPP are manufactured in dumbbell specimens with 75 ton DFFIM machines. In DFFIM, 1200 Tex of GF is supplied to the DFFIM vent barrel. The matrix feed rate was set at 50 rpm and the fiber filling rate was set at 30%. Mechanical properties and morphology of GFPP composites with DFFIM are characterized by tensile test, impact test and scanning electron microscope (SEM). The center of the dumbbell specimen is cut and fired at 600 ℃. in a furnace. Weigh the remaining fibers and measure the volume fraction of the fibers.