Abstract: The compound with low molecular weight is thought to play a key role in the structure of coals and has a significant effect on the process of coal pyrolysis. The purpose of this paper is to describe the characteristic of pyrolytic process of extract. The sample was obtained from vitrain extracted by tetrahydrofuran. The thermal decomposition behavior of vitrain and its extract were investigated by TG and Py-FTIR, the latter can continuously obtain IR spectra of the volatiles as the sample is heated. The TG and DTG curves of extract are different from those of vitrain. The rate of weight loss of extract is higher than that of vitrain. Two peaks in DTG curve of extract were observed at 190 ℃ and 452 ℃ individually, while no peak was observed at 190 ℃ for vitrain. The maximum peak in DTG curve moves towards low temperature compared with vitrain. The results of Py-FTIR shows that the amounts of aliphatics evolution of extract is higher than those of vitrain, the evolution profile indicates the evolution of aliphatic compounds is fast. The amounts of methane and CO2 evolution from extract were lower than those of vitrain, no CO was produced from extract.