Forest fire is a ubiquitous natural process that affects the function and structure of an ecosystem. How does forest fire affect the quantity and quality of soil organic matter (SOM) is one question needs to be answered. We initiated this study to investigate the change of SOM in response to the frequency of prescribed fire with special reference to the quality of SOM. We took the advantage of the long-term prescribed fire experiments of the Tall Timbers Research Station since 1966 and the newly developed multi-elemental scanning thermal analysis (MESTA) technology to carry out this study. Soil samples from three depths (0-5, 5-10 and 10-20 cm) of the no-burn (NB), burned every three years (3B) and burned every 9 years (9B) plots were taken, air-dried, sieved through 2 mm sieve and analyzed using MESTA to characterize the SOM. The MESTA device heats up a sample from 35 to 80 ^oC under 33 % oxygen and 67 % helium as carrier gas. The volatile is then oxidized in a high temperature combustion tube under pure oxygen and C, N and S detected by the respective detectors. The results are simultaneous C, N and S thermograms of the sample which show the amount of C, N and S with respect to their volatilization temperature. Preliminary results of this study show that frequent prescribed fire did not reduce the amount of SOM in the plot. All the SOM show two major components of organic matter: one volatilized around 300 ^oC and the other around 450 ^oC. The SOM of prescribed fire plots have relatively more high-temperature component than that of the no-burn plot. Fire did not increase the black carbon content of the soil in the 3B and 9B plots than NB plots.