FRP Composites are lightweight, strong materials used in the manufacturing of numerous products used in our daily life. In general, Carbon Fiber Reinforced Thermoplastic called CFRP composites use thermosetting resins. Not only are carbon fiber composites lighter weight, but CFRP composites are much stronger and stiffer per unit of weight. Carbon Fiber Reinforced Thermoplastic Composites use in injection molding can short output time and get complicated product shape. This slider is materials and effect of fiber length on mechanical properties when the fiber is longer the mechanical property is better The neat thermoplastic, SFT, were used in conventional injection molding In future, the LFT, CFRT-Woven, CFRT-UD will be popularize in the thermoplastic injection molding. We say the fiber length is over 10 mm, the number is magic number Because if the fiber length is over 10 mm, the mechanical property stiffness and strength performance is very good. This feature let using plastics replace the Steel is possible and the market will focus on automobile industry. This is in line with our technological development and closely follow the relevant technology.