Abstract: The functional group contents of 18 rank Chinese coals were studied by the chemical analysis and the FTIR spectrum's anaysis. The results show that: the functional groups in coal are the function of coal rank, and the yields of CO 2, H 2O and CO are related to the content of carboxyl, hydroxyl and other oxygen containing groups such as ether groups in coal, and Tar and CH 4 are related to the aliphatic CH, the char yields to the aromatic CH. It's suspected that the coal pyrolysis is the functional groups decomposition.