Based on the results of Fourier Transform Infrared Spectroscopy (FTIR) test of surface functional groups of different coal samples in low-temperature oxidation, the quantitative variation between functional groups and temperature was analyzed by B-mode grey relational analysis. According to the grey B-mode degrees and orders, a summary is given that: 1)the aromatic ketone and aldehyde carbonyl groups are mostly produced during the process of coal oxidation and the oxygen-containing functional groups existed mainly in the form of stable ether bond; 2)the methylene groups make major contribution to coal spontaneous combustion, so that the methylene structures should be disposed firstly in order to suppress coal spontaneous combustion effectively; 3)the degree range of gas coal is the largest, which shows that the process of gas coal spontaneous combustion is mostly affected by active groups to some extent. These quantitative results will be helpful to find the functional groups affecting deeply the process of low-temperature oxidation of coal.