Abstract: 3D five-directional fabric show great promise for aerospace applications owing to their high specific strength, high specific modulus, and excellent axial properties. However, there is a dearth of research on their mechanical properties and failure behavior at high temperature environments. The quasi-static tensile mechanical behavior and failure mechanism of aluminum matrix composites reinforced by 3D five-directional fabric at high temperature (300℃) were studied. According to the fabric structure and yarn microstructure, the finite element model of microscopic mechanics based on representative cells of microscopic and microscopic scales were established. The macroscopic mechanical response, damage and failure behavior of the components during the high temperature tensile process were analyzed according to the numerical simulation and experimental results. The tested tensile modulus, strength and fracture strain of the composites are 137.75 GPa, 745.9 MPa and 0.659%, respectively. The tensile stress-strain curve predicted by the micromechanical model generally agrees with the experimental curves. Under the high temperature, there exists the complex thermal stress distribution in the composites, where the tensile stress of the braiding yarns are higher than that of the stationary yarns, and the compressive stress of matrix is relatively homogeneous. In the initial tensile stage, the local yarn and interface failure at the interweaving of the braiding yarn and the axial yarn; however, the composite exhibits a linear elastic response. As the tensile load increases, obvious interface delamination failure emerges between the braiding yarn and the axial yarn. The ability of the composite to resist deformation declines and demonstrates nonlinear macroscopic mechanical responses. In the final stage, the interface undergoes extensive delamination, and the braiding yarn and the stationary yarn break down successively, leads to catastrophic fracture of the composite, resulting in a dramatic drop of the tensile stress. The fracture surface presents a microscopic morphological characteristic where fiber fracture pulling out and metal alloy tearing strips coexist.