It is hard to distinguish the type of hydrogen bonds formed by hydroxyl groups by normal FTIR methods because of the interference of water in samples. In this work, a method is proposed for the clear observation of the types of hydrogen bonds by FTIR. The method involves the evaporation of water in a vacuum chamber with CaF2 windows (vacuum level, 4 x 10(-3) kPa) followed by in situ scanning of the IR spectrum. Five types of hydrogen bonds were found in coal and its extracts. The hydroxyl groups in coal mainly exist as self-associated OH and OH-N hydrogen-bonded pairs. The thermal stability of these hydrogen bonds was investigated by means of in-situ pyrolysis FTIR. It follows the order of OH-ether O > self-associated OH x cyclic OH > OH-N > OH-pi.