The transient distribution of the temperature field is a crucial indicator for assessing the extent of explosion damage. Explosions, detonations, and other phenomena that occur during a fire can pose significant risks to emergency rescue operations. It is necessary to study the changes in the transient temperature field during the explosion process and the extent of damage. It can improve the safety of fire extinguishing. The distribution range and temperature values of the transient temperature field during the explosion process were quantitatively analyzed. A radiation temperature measurement system based on spectral normalization was designed. The existing literature primarily employs radiation thermometry to measure the temperatures of flames from explosions. Most literature uses a single wavelength to calculate the brightness temperature field within the explosion zone. But this method cannot calculate the true temperature value. A structure for image acquisition based on a multi-wavelength combination narrowband filter partition has been designed. A spectral normalization radiometric temperature measurement algorithm was proposed. The system consists of an imaging lens group, a multi-wavelength combination narrowband filter, and a multispectral camera. The imaging lens group is used to collect explosive radiation from the test area and achieve collimation and focusing. A multi-wavelength combination narrowband filter is a combination of four narrowband filters with different characteristic wavelengths. It enables simultaneous acquisition of images on the photosensitive surface of the CCD array. This design sacrifices 1/4 of the spatial resolution in exchange for simultaneously obtaining test images of four characteristic wavelengths. Finally, the multispectral camera simultaneously captures multispectral images under four characteristic wavelength conditions. The processing module is used to complete temperature inversion based on radiance. Finally, obtain the temperature field and transient changes within the explosion area. The experiment utilized the S16 thermocouple sensor to calibrate the instantaneous temperature at the actual location of the explosion area, and the M20 infrared thermal imager's test results were used to calibrate the transient temperature range in the explosion area. The temperature test results of the thermocouple sensor show that the highest temperatures at distances of 1.0 and 5.0 m are 1 625 ℃ and 810 ℃, respectively. The inversion results of this system are 1 602 ℃ and 783 ℃, respectively, with an average relative error of 3.1%. The range test results of the thermal imager show that the maximum range is 6.9 m×6.0 m. This system is 7.2 m×6.3 m, with an average relative error of less than 5%. It verifies the feasibility of using four characteristic wavelength partition images to invert the instantaneous temperature field of the explosion area in this system. The experimental results demonstrate that the transient temperature inversion accuracy of this system is high, enabling it to reconstruct the three-dimensional temperaturefield. This design can dynamically identify the explosion range. It has greater potential and practical value in fields such as fire and explosion.