Abstract: The mechanism of the solid-state polycondensation of nylon-66 with carbon fiber composites and effects of the interface between the fiber and matrix were studied by using polarized light microscopy, SEM and thermal analysis methods (DSC,TGA). It was found, that some inter-facial effects such as fiber surface nucleating the crystallization and catalytic effect for the “in situ solid-state polycondensation” of nylon-66 salt were existed. The interfacial effects of the carbon fiber on the epitaxial crystallization and melt behaviour of nylon-66 matrix as well as on the stabilization for thermal oxidation of nylon-66 matrix have been discussed.