<p>Thermal insulation performance of foam concrete is significantly influenced by the porous structure characteristics which can unveil the heat transfer properties. To investigate the pore structure characteristic parameters effects on the thermal conductivity of foam concrete and to explore internal heat transfer behavior, experimental tests were conducted to analyze pore structure characteristics and thermal conductivity. Further, COMSOL software was employed to create a porous media model and to explore the influences of porous structure on heat transfer processes and the heat flow behavior. Furthermore, a method to improve the thermal insulation performance of ceramsite foam concrete is proposed. The results indicate that, the OPC-CE、OPC-CSA and OPC-CSA-PP composite cementitious systems were, significantly, reduced in the porosity of pores larger than 400 μm. The pore distribution in the OPC-CE composite cementitious system is more uniform compared to the control group. Furthermore, the addition of the OPC-CE and OPC-CSA composite cementitious systems, along with PP fibers, can significantly reduce the thermal conductivity of foam concrete. Numerical results suggest that compared to small pores, heat tends to flow more from larger pores. This indicates that foam concrete with consistent porosity but higher small pore porosity showcases lower thermal conductivity, thereby enhancing its insulation performance.</p>