Carbon fiber (CF) was widely used for advanced composite fields such as transportation due to their various advantages of high strength and stiffness, etc. Also, polyimide (PI) was high performance polymer having dimensional stability, heat resistance and mechanical properties etc. In this study, CF non-woven was prepared by wet-laid process. And the composite materials based on CF non-woven with multilayer structure were prepared by vacuum assisted resin infusion (VaRI) molding technique with the use of PI to improve its mechanical and thermal properties. Two different molecular weights of PI have been used in the PI-CF composites. The thermal stabilities and mechanical properties of PI reinforced CF composites were investigated using several methods. Field emission scanning electron microscopy (FE-SEM) and fiber volume fraction of composites were adopted to characterize the morphology and structure properties. The obtained results showed that mechanical properties of composites using CF non-woven with multilayer structure were improved better strength than that of single or few layer composites. The morphology of PI resin in CF non-woven matrix indicated good degree of dispersion.