Abstract: Pyrolysis, as a method of precombustion desulfurization of coal, is an effective approach to control SO2 emission in clean coal utilization. In this study, Yanzhou (YZ) coal was pyrolyzed in a fluidized bed reactor under 3.0%, 5.6% and 8.7% O2 N2 atmospheres and at the temperature range from 400℃ to 800℃. The sulfur distribution in gas and tar product was analyzed. The optimal desulphurization result with 3% O2 N2 atmosphere at 600℃ is reached, during which about 97% pyrite sulfur and 60% organic sulfur are released. However, under N2 atmosphere, at the same temperature, the desulphurization ratio of total sulfur and organic sulfur is only 25% and 15%, respectively. Under the oxidative atmosphere, the most of sulfur in coal is transferred into tar. With increasing the oxygen content of atmosphere, the char yields decrease quickly at high temperature. The decreasing degree of char yield is higher than the increasing degree of desulphurization rate. This suggests that the higher oxygen content would break C—C bonds severely when selectively breaking C—S bonds.