Infrared thermal imaging technique is a new method for detecting the fire source. But a number of problems have to be solved before it can be applied to the detection of a spontaneous fire source of sulfide ores in mine. In order to determine the surface temperature of spontaneous combustion ores more accurately, preliminary studies were carried out on the effects of emission rate, the range of the detector, background noise, subsurface environment and stability of infrared thermal imagers. It is shown that the emission rate of materials and the range of the detector have greater influence on the precision of the measured temperature than other factors. Some measures are taken to control factors, such as background noise, subsurface environment and stability of infrared thermal imagers in order to avoid external disturbance and keep the imager stable. The emission rate of sulfide ores and the reasonable range of IRI-1101 infrared thermal imagers were determined based on experimental results and a theoretical analysis. The emission rate of sulfide ores is ε=0.88. Within 10m, the temperature error will increase greatly with the measuring distance. When the temperature of the heat source is kept in a certain range, the temperature error is almost linearly related with the distance at 3m and 4m. Temperature error is stable at 2m when the temperature of the heat source T>50℃. The quantitative relationship between the temperature obtained by IRI-1101 infrared thermal imager and the real surface temperature of spontaneous combustion ores was established when distance is equal to 2m, 3m and 4m, respectively. After the adjustment, the relative error of four measuring points are -3.1%, 3.9%, 5.5% and -5.8%, respectively. The results of study were confirmed by field tests in the sulfide mine.