Abstract: The functional groups characteristics of two different degrees of metamorphic coal were quantitatively studied using FTIR spectrometry and curve-fitting technique. Some structure parameters have been applied to evaluate the differences in chemical structures of coal. The results show that the content of organic matter in low rank coal is relatively small. In the process of transformation from low to high-rank coal, the maturity of organic matter increases, so that the skeleton of the coal becomes soft. The side chains of alkyl become longer and branched chain becomes lesser. With the increase of coal rank, the content of oxygen-containing functional groups decreases. Meanwhile, the degree of the aromatic ring condensation becomes higher. It is feasible to quantitatively study the chemical structure of coal by Fourier transform infrared spectroscopy and curve-fitting technique.