Abstract: Chinese Xundian, Mongolian Shiveeovoo lignites and Khoot oil shale are pyrolyzed under synthesis gas (SG) at temperature range from 400 ℃ to 800 ℃ for lignite and from 300 ℃ to 600 ℃ for oil shale with heating rate of 10 ℃／min in a fixed bed reactor. The results were compared with those obtained by pyrolysis under hydrogen and nitrogen. The results showed that unlike pyrolysis at high pressure, there are only slight different in the yields of char and tar among pyrolyses under various gases at room pressure for lignite, while higher liquid yield with lower yields of char and gas was obtained in pyrolysis of oil shale under SG and H2 than under N2. It is found that the pyrite S can be easily removed to partially convert to organic S under various gaseous atmosphere and the total sulfur removal for oil shale is much less than lignite, which might be related to its high ash content. The higher total sulfur removal and less organic S content in the presence of SG in comparison with those under N2 and even under H2 in pyrolysis of Xundian lignite might result from the action of CO in SG. However, CO does not show its function in pyrolysis of Khoot oil shale, which might also be related to the high ash content. The results reported show the possibility of using synthesis gas instead of pure hydrogen as the reactive gas for coal hydropyrolysis.