A single-wavelength pyrometer used for evaluating the effects of thermal damage was developed,which offered a new method to describe the temperature changes of explosive products during the course of the explosion. The temperature of oxyacetylene flame was simultaneously measured by the pyrometer and a thermocouple. And the measurement error of the single-wavelength pyrometer is only 6.2%. The results indicate that the emissivity has little effect on temperature measurement of the oxyacetylene flame by the pyrometer. The pyrometer was aslo used to measure explosive products temperature of TNT. The curve of thermal damage of TNT was obtained,which shows the temperature changes of the explosive products of TNT,and the peak temperature of the curve is 3167.15 K.