Abstract: Fiberglass/epoxy honeycomb sandwich composites have become the main materials for interior wall panels of civil aircraft due to their light weight and excellent flame retardant properties. These materials are fire hazardous at high temperatures, so the study of their thermal conductivity is of great significance for aircraft fire protection. Nine kinds of honeycomb sandwich materials with different thicknesses were prepared from glass fiber/epoxy resin prepreg and aramid paper honeycomb core to carry out the thermal conductivity study. Based on Fourier's law and the semi-empirical formula of Swan-Pittman, a theoretical model of heat transfer of fiber-reinforced resin matrix composites was established, and the theoretical value of thermal conductivity of honeycomb sandwich materials was calculated based on the data obtained from the simulation of Finite Element Software. Based on the data obtained from the finite element software simulation, the theoretical value of thermal conductivity of the honeycomb sandwich is calculated. The thermal conductivity tester is used to carry out experiments on the thermal conductivity of honeycomb sandwich materials and compare the experimental and theoretical values. The results show that the theoretical values of the thermal conductivity of honeycomb sandwich materials with different thicknesses at room temperature are in good agreement with the average values of the experiments, and the theoretical model is applicable to the fiber-reinforced resin matrix composites with honeycomb sandwich structure; compared with the thickness of the panels, the honeycomb core is the main factor affecting the thermal conductivity of honeycomb sandwich materials. The porosity of the honeycomb sandwich material is inversely related to the thermal conductivity, and the specific surface area is positively related to the thermal conductivity; with the increase of the height of the honeycomb core, the thermal radiation replaces the thermal conduction to become the main way of heat transfer inside the honeycomb core gradually.