Abstract: Pyrolysis of three high rank coals, Changcun, Rujigou and Jincheng, were investigated by TG, and the evolved hydrogen was on-line analyzed by mass spectroscopy. The results show that Rujigou and Jincheng coals have higher initial pyrolysis temperature, higher temperature of maximum weight loss rate and lower maximum weight loss rate. This indicates that the macromolecular structure tends to be stable with the increase of coal rank. Analysis of the evolution characteristics of hydrogen indicates that the initial temperatures (t0) of hydrogen evolution increases with the increase of carbon content. The maximum rate temperature (tmax) is the highest for Changcun coal. This maybe relates to the low aromaticity of Changcun coal. The condensation between the aromatic hydrocarbons will occur up to higher temperature. The evolution intensity of hydrogen from Changcun coal is obviously higher than that for Rujigou and Jincheng coal.