Abstract: The surface of carbon fiber (CF) was modified by aminosilane coupling agent and introduced into polyamide 66 (PA66) resin. XPS, SEM, DMA and mechanical performance tests were used to characterize the structure and properties of the interface of composites. The effect of carbon fiber surface modification on the properties of the composites were studied. Results showed that the surface active functional groups increased after modification, such as the content of O—C＝O and C＝O, which were increased by 95.24% and 508.45% respectively. The surface modification increased the surface roughness of carbon fiber and enhanced the bonding strength between the fiber and the thermoplastic resin. The addition of modified carbon fiber improved the mechanical properties compared to virgin carbon fiber. Simultaneously, the flexural strength and modulus were increased by 30 MPa and 424 MPa respectively, and impact strength was increased by 6 MPa. The storage modulus increased significantly, and the glass transition temperature increased nearly 5℃.