Abstract: Conformal antennas, due to their capability of integrating electromagnetic functionality, structural support, and lightweight design, exhibit greater adaptability to modern development trends compared to conventional airborne antennas. However, sandwich structures utilizing composite materials with multiple layers and materials possess inherently weak interlayer load-bearing capabilities. Embedding antennas within these structures significantly alters their load-carrying characteristics and structural failure modes due to the introduction of new interfaces. Furthermore, uncertainties arise regarding whether the structure can fulfill design requirements following changes in manufacturing technology and forming process. This paper focused on the bearing characteristics and failure mechanisms of a conformal antenna sandwich structure (CASS) under lateral pressure loads, employing both experimental and finite element analysis methodologies. We benchmarked our findings against a composite foam sandwich structure (CFSS) for comparison. Our results reveal that incorporating the antenna interface increases the structural weight by 38.87%, enhances the specific strength by 1.35%, but diminishes the specific stiffness by 21.72%. Notably, the introduction of the antenna array shifts the structural failure mode from a central fracture dominated by layered progressive failure to a progressive matrix compression failure extending along stress concentrations at the clamping ends of the fixture. Additionally, the CASS processing technology encounters glue overflow issues, and the uncontrollable degree of overflow can modify the load-bearing and failure mechanisms of the structure. Thus, mitigating glue overflow becomes pivotal for optimizing the mechanical properties of the CASS.