High-strength and lightweight are two of the most important parameters for composites in the construction field. Here, we developed a novel foam concrete structure with sandwich porous structure by using in-situ polymerized polyacrylamide and ultra-stable foam, which can obtain higher mechanical strength in comparison to the normal porous concrete with the same density. The ratio of stiffness to weight was maximized to achieve the optimal sandwich porous structure size. The SEM images showed that the interface bond between the foam concrete and the polymer modified cement paste was tight and robust. The flexural strength of the novel structure was 65.6% higher than that of the foamed concrete at the same density. The series model was established to calculate the composite thermal conductivity of the novel foam concrete structure, indicating that the heat insulation was slightly improved compared with the normal foam concrete. Moreover, water resistance displayed a slight increase by constructing this sandwich porous structure. Hopefully, the novel composite with sandwich porous structure can put a new way for designing the lightweight and high strength insulation thermal structure.