Abstract: The preparation and mechanical properties of glass fiber 3D fabric reinforced epoxy foam composites (GF-Fabric/EP composites) were studied in order to further improve the bearing capacity and comprehensive properties of foam sandwich composite materials and realize its application in rail transit and automobile industry. The GF-Fabric/EP composite and its sandwich structure were fabricated. The failure behavior of GF-Fabric/EP composite and its sandwich structure were explored to reveal the reinforcing mechanism of the 3D fabric. The results show that the introduction of 3D fabric can significantly improve the strength, stiffness and failure strain of GF Fabric/EP composites. However, under different load-bearing conditions, each yarn plays a different role and effect. The properties, dimensions and surface/core interface properties of panel and core materials are important factors affecting the mechanical properties and failure characteristics of GF Fabric/EP sandwich composites. Taking the bending properties under three-point loading as an example, for different GF Fabric/EP sandwich composites, it is necessary to adjust the span thickness ratio and specimen size and obtain ideal failure characteristics before effective and reasonable evaluation of their bending properties or interlaminar shear properties.