Abstract: Five oil shale kerogens from different regions were analyzed by KBr-FTIR spectra, and a quantitative determination method of structural parameters of kerogen aliphatic hydrocarbon was established by peak-fitting analysis. Thermogravimetric (TG) and Fourier transform infrared spectroscopy (FT-IR) analysis was used to online analyze devolatilization components of kerogen pyrolyzed at 20 ℃/min. The reactivity characteristic and variation of structural parameters of aliphatic hydrocarbon with pyrolysis time were obtained. The results show that the oil shale kerogen was composed of aliphatic hydrocarbon, aromatic hydrocarbon and oxygen functional groups. The relative content of aliphatic hydrocarbon structure, mainly long chain methylene, reaches 18.5%~78.2%. With increasing degree of kerogen evolution, the content of aliphatic hydrocarbon and capacity of oil generation decrease. The decomposition of kerogen mainly occurs during 350~520 ℃. The thermal weightless is mild when above 520 ℃ at which mass fraction of the residual char is 19.5%~52.2%. FT-IR analysis shows that free water releases out firstly during pyrolysis, subsequently depolymerization and dehydration reactions occur, and in which main side chains of alkane fall off and cyclization and oxygen-containing groups break into various of hydrocarbons, acids, alcohols, aldehydes, etc. until more stable graphite-like structure is formed.