Oil shale is a potential substitute fossil fuel for petroleum and gas and has attracted much attention in recent years. This study investigated the pyrolysis characteristics of LongKou oil shale in a horizontal pipe furnace, and the gas production and functional groups in coke when different amounts of pyrite were added. The results showed that the organic matrix was decomposed completely in the optimal conditions (a temperature of 500 degrees C, a gas speed of 300 mL/min and a resident time of 40min). For aromatic hydrocarbon, substitution can be promoted in the direction of H-decrease by the presence of pyrite. For aliphatics, pyrite will inhibit the condensation of macromolecules causing an increase of aliphatic chain length. For O-containing groups, carboxyl was consumed completely and the ratio of C =O to aromatic carbon was decreased. And for gas products, pyrite can promote the generation of CO2, CO and CH4 on the whole. But it is worth mentioning that when the content of pyrite is suitable (2%), generation of all gases especially CO and CH4 is promoted significantly. Considering the pyrite is an important part in untreated oil shale, the results obtained in this research may be able to provide some useful information for desulfurization and gas production in oil shale retorting.