Compared with traditional materials, carbon fiber reinforced thermoplastic composites (CFTRP) have higher toughness and deformation recovery ability, and are more conducive to recycling, and widely used in aerospace, automotive ship and other fields of the main bearing components, for its mechanical properties and failure mechanism have become a current hot direction. However, most of the researches have neglected the influence of the interface between fiber and matrix on the overall mechanical properties of composites. In this paper, taking the polyether ether ether ketone (PEEK) /T700 carbon fiber-reinforced composites as the object of research, the representative volume element (RVE) considering the interface and disregarding the interface is established by combining the method of experiments and finite element analysis, respectively. The influence of the interface on the mechanical properties and failure modes of the composites is systematically investigated by applying loads in various directions to them. The results indicate that the RVE considering interface behavior provides more accurate predictions of the composite strength and failure modes. Among these, the prediction accuracy for transverse tensile strength shows the most significant improvement, and the improvement for in-plane shear strength is more modest. The results and patterns can provide a reference for the structural design and performance evaluation of high-performance thermoplastic composites in practical engineering applications.