The relevance of the research. When simulating the combustion processes it is often necessary to determine the temperature field. Traditional methods of experimental studies of combustion processes involve the use of a large number of thermocouples to determine the temperature fields in the flame, which causes difficulties in determining the temperature. The thermocouple determines the temperature not in a specific point of the space, but in a region with radius about ten diameters of a thermocouple. When using the thermo" couple method, one should consider the inertia feature and heat flow over the free ends. Modern methods of infrared diagnostics with application of thermal imaging cameras allow abandoning the use of a large number of thermocouples and obtaining the acceptable spatial resolution with high time details. The methods used in the study: The paper deals with the experimental study of temperature change in the flame. The flame genera" ted at combustion of different fuels was selected as the test object. The combustion was shot with a thermal imaging camera in different spectral ranges. At the same time, the temperature in the flame was controlled with a thermocouple; the emissivity was corrected by the data from the thermocouple. On the thermogram obtained the authors have selected 20 points on the same vertical axis. For each point the array of temperatures was obtained. The fast Fourier transform was applied to the array. The authors obtained the frequency" amplitude spectra of temperature change. The results. The typical temperature surges were identified. To investigate liquid fuels the frequency maximums are ranged from 4 to 16 Hz, for vegetative combustible materials the frequency peaks were found in the range from 2 to 7 Hz.