The polylatic acid(PLA) extracted from corn, potato and sweat potato have been popular bio-composite since it is able to be decomposed into the nature environment easily. But since the PLA of bio-composite have the low mechanical strength and specific thermal property it is limited to use it in the marine industry and airplane industry to require high mechanical performance and high thermal expansion. Therefore, to improve these specific properties of PLA composite it is needed to be composed with other composite materials than using PLA only. In this study, the effects of SiC contents of PLA/SiC composite were investigated on the different SiC contents through the tensile test of ASTM D 638. The manufacturing process of extrusion and injection was applied to manufacture the PLA/Sic composite. The diverse SiC contents of 5%, 10%, 15% and 20% were mixed with PLA by using twin screw extrusion. Finally, the experimental results showed the different SiC contents didn’t affect the tensile strength of PLA/Sic composite especially.