Abstract: In order to research the reliability of high strength polyethylene under high temperature conditions and the heat insulation properties of SiO₂ aero-gel and ceramic cotton, the SiO₂ aero-gel blanket/ceramic cotton with high strength polyethylene integrated structure scheme with no clearance was put forward. The standard fire test was performed on the structural unit. The failure mode of the refractory material and the influence law of refractory thickness on the sandwich structure were analyzed. The study discusses the practicality of area density and the overall thickness of the structure on the premise that the composite structure bulkheads satisfies the refractory requirements. The results show that the advisable thickness of the SiO₂ aero-gel blanket and ceramic cotton each have good refractory insulating performance, and the thermal protection effect of the composite bulkhead structure is obviously improved with the higher thickness of the insulating layer. To achieve the same effect, less SiO₂ aero-gel blanket is needed than ceramic cotton; the SiO₂ aero-gel blanket is superior when considering area density and whole structure thickness; and the ceramic also has a certain insulating effect when added to the sandwich structure. As such, the integrated optimization of the composite bulkhead structure can effectively improve the protective performance of marine bulkheads.