Mercury (Hg) is a volatile and toxic trace element in coal. Its emission to the environment can cause long-term contamination problems to human health and the environment. In this study, Hg in six Chinese coals from different ranks was characterized by temperature-programmed decomposition atomic fluorescence spectroscopy (TPD-AFS) and acid-leaching techniques. The results show that TPD-AFS is an effective method to assist the characterization of Hg in coals. With the aid of acid leaching, the thermal behavior of the grouped Hg-containing components can be obtained. Generally, the content of organic-bound Hg is in the range of 16-36% and releases in the temperature range of 220-600 degrees C. The content of silicate-bound Hg is in the range of 10-26% and releases in the temperature range of >600 degrees C. The content of pyrite-bound Hg is in the range of 5-44% and releases in the temperature range of 250-630 degrees C. The content of HCl-soluble Hg is in the range of 10 34% and releases at the lower temperature range. The thermal behavior of Hg from the coals tested shows a certain dependency upon coal rank.