The pyrolysis characteristics of macerals separated from Chinese Shenmu coal were systematically investigated using TG-151 pressurized thermobalance coupling with mass spectrometer under 0.1 MPa of Ar and H-2, heating rate of 10 degrees C/min and final temperature of 900 degrees C. The TG/DTG results showed that vitrinite always had a higher volatile matter yield, larger maximum rate of weight loss, lower temperature of the maximum rate of weight loss than inertinite. Inertinite showed high response to the external hydrogen, especially at a higher temperature. The gases evolved during thermogravimetric analysis of macerals were analyzed on-line by mass spectrometer for the relative intensity of H2O, C-1-C-4, and C6H6. An obvious difference in evolution curves could be observed. The content of all gases evolved from vitrinite was higher than those from inertinite in both atmospheres. The amount of H2O and light hydrocarbons was higher in H-2 than that in Ar, indicating the hydrogenation of oxygen-containing functional groups and free radicals formed during pyrolysis. The evolution curves of H2O and CH4 had different peak distributions and evolution temperatures under H-2 and Ar, suggesting the different reaction mechanism during pyrolysis in different atmosphere. The evolution curves also revealed the different structural characteristics among vitrinite, inertinite and the parent coal.