Abstract: Carbon nanotubes (CNT) are widely used in composites because of their excellent mechanical properties, such as light weight, high strength, and stable chemical properties. In order to explore the reasons for the difference in mechanical strengthening effects of different matrices, in this paper, quasi-static tensile, bending tests and dynamic impact test were carried out on CNT composite resin matrix and aluminum alloy matrix, and the reinforcement mechanism of CNT in different matrices was further revealed. The results show that CNT could effectively improve the tensile strength and energy absorption properties of resin materials, and when the CNT content (mass ratio) was 0.7%, the reinforcement effect was the best. For aluminum alloy, the addition of CNT would reduce the strength of the material, and the higher the content of CNT, the lower the tensile strength of the material. The essence of the different mechanical strengthening effects of metal matrix and resin matrix after adding CNT lied in the different interfacial bonding between CNT and matrix. The initial state of resin matrix was liquid; after curing, CNT could be filled in the matrix network gap, so as to enhance the mechanical properties of materials; the aluminum alloy matrix was powder, and the dispersion of mechanical force caused CNT damage, and the existence of CNT caused the gap between the powders to become larger, weakening the mechanical properties of the material. The research results of this study provide a theoretical reference for subsequent research and development of a variety of matrix particles and fiber-reinforced composites.