The heat-resistant and high-temperature insulation properties of Al2(SiO3)3 fiber/phenolic resin composite material were investigated, and meanwhile a numerical solution to the heat conduction process containing chemical heat effects of a hermetical system with multilayer different heat insulation materials in high-temperature environment was searched. Al2(SiO3)3 fiber/phenolic resin composite was prepared for heat insulation in the hermetical system, and the active high temperature resistant heat insulation goal of the material was achieved through the endotherm feature of the phenolic resin decomposing at high temperature. The heat insulation properties of the hermetical system with multilayer adiabatic materials were investigated through the fire test. Therein the hermetical system was fabricated with 20 mm thick Al2(SiO3)3 fiber/phenolic resin material, and the temperature on the back side of the high temperature resistant adiabatic material was tested during the fire test to investigate the heat insulation property of the material. On the assumption that the decomposing heat of the phenolic resin is equivalent to a heat resource in the multilayer adiabatic system containing chemical heat in hermetical system, the heat conduction mathematic model of the hermetical system was established. The Matlab Partial Differential Equation Solver was employed to solve the problem numerically. The numerical results were compared to the test temperature to verify the accuracy of the calculation results. After 120 min of sided ablation in open system, the back surface temperature of Al2(SiO3)3 fiber/phenolic resin composite material with a thickness of 2 cm kept below 140 ℃ and there was no sign of damage. As measured in the fire test, the endotherm feature of thermal decomposition of the inorganic high-temperature resistant adiabatic material extended the heat penetration time, and the maximum deviation of the numerical solution of the heat conduction model in hermetical system from the test result was 37%. Al2(SiO3)3 fiber/phenolic resin composite material has good ablation resistance and high-temperature heat insulation property, and the heat equivalence hypothesis is reasonable and practical in solving the heat conduction problem in heat-insulating system with chemical heat effects.