In this work, several typical organic sulfur model compounds, including thiophenic and dibenzothiophenic sulfur: and one Chinese coal, Wujiaping, with more organic sulfur were pyrolyzed under 1.0% O-2/Helium (He) and the sulfur forms released were detected by on-line mass spectroscopy in order to investigate the effect and the mechanism of low concentration of oxygen on the removal of the stable organic sulfurs in coal in view of model compounds. The results show that the specific peak temperature of sulfur release is decreased during pyrolysis of the stable thiophenic sulfur model compounds under low concentration of oxygen compared to that under inert atmosphere. It indicates that the low concentration of oxygen has a positive effect of on removal of the stable sulfur: When Wujiaping coal is pyrolyzed under 1.0% O-2/He, the peak temperature of SO2 is always: lower than those of CO? and CO, indicating that the oxidation of sulfur occurred before that of the organic carbon frame of coal. The coal pyrolysis lest showed that the low concentration of oxygen could increase the efficiency of sulfur removal while the char yield could not be decreased remarkably.