More and more attention has been paid to the thermal damage in explosion field recently. In view of the abominable test environment of explosive field, a new type of an infrared flux density sensor is designed. This sensor uses its thermal sensitive element to be in direct contact with the explosive product, then the thermal element rises in temperature to produce infrared radiation, and based on the principle of infrared temperature measurement, the temperature rise of the heat sensitive element is obtained, finally, the heat flux can be indirectly obtained by the mathematical model theory of heat conduction. Compared to conventional heat flux sensors, this new type of heat flux sensor has fast response time, wide testing range and high measurement accuracy, it can be used in thermal damage test and evaluation of explosion field effectively.