To understand the thermal response behavior of the structure with explosive under fire circumstance, in view of some related main heat transfer problems, the numerical models of pool fire′s temperature rise heat transfer, carbon/bakelite ablatant′s high temperature endothermic decomposition, inner air layer′s complex heat transfer and explosive′s exothermic decomposition were established. The thermal response and thermal ignition delay time for the structure with explosive under the conditions of different temperature (constant value 1073 K, 1273 K, and measured temperature rise curve proposed in this work), different fire′s emissivity (0.1-0.9) and different surface emissivity for the shell with different air gap (0.1-0.9) were calculated and obtained using the established numerical models. Results show that the thermal ignition phenomenon of the inner explosive occurrs at 28.92 min when the fire′s temperature is 1273 K in 30 min fire case. The highest temperature of inner explosive is 448 K and 535 K, respectively when the fire′s temperature is 1073 K and real temperature rise curve. The highest temperature of the explosive decreases from 535.5 K to 344.6 K and the thermal ignition delay time increases from 1917 s to 3520 s when the fire′s emissivity reduces from 0.9 to 0.1. The highest temperature of the explosive decreases from 535.5 K to 329.0 K and the thermal ignition delay time increases from 1917s to 3739s when the surface emissivity for the shell with air gap reduces from 0.9 to 0.1.