To understand the underground combustion state during the fire flooding development of Du66 Block，we worked out a new method to identify the combustion state during fire flooding. Three production wells were selected to carry out the follow-up monitoring of crude oil and tail gas for five years. The gas chromatographic fingerprint technique of crude oil and the multi-dimensional gas chromatographic technique of tail gas were used to study the fingerprint characteristics and parameters of crude oil and tail gas of high-temperature oxidation during fire flooding in the production field. The results show that the chromatographic fingerprint of n-alkanes of crude oil is featured by forward main peak carbon，higher lighttoheavy ratio，increased content of light hydrocarbons，isoparaffins，and n-alkanes after high-temperature oxidation in the fire flooding production site. The chromatographic fingerprint of isoprenoid hydrocarbons shows reduced Ph/nC17 and Pr/nC18；the content of iC21 is nearly the same as or less than that of nC19. Oxygen conversion，apparent hydrogen-to-carbon atomic ratio，and carbon-dioxide content in tail gas are effective parameters for the high-temperature oxidation of fire flooding.In addition，cracked components such as olefins and hydrogen appear in the multi-dimensional chromatographic fingerprint of tail gas.