Abstract: Yima (YM) coal and Pingshuo (PS) coal as well as their deashed coals and depyrited coals were used to investigate the effects of CO₂ and Ar on the sulfur release behavior during coal pyrolysis by pyrolysis connected with mass spectrometer (Py-MS) and pyrolysis connected with gas chromatogram (Py-GC). It is found that CO₂ atmosphere can promote the release of H₂S, COS and SO₂, especially the remarkable releasing of COS. In addition, CO₂ atmosphere can decrease the maximum release peak temperature of H₂S, COS and SO₂ for raw coals, while there is no obvious effect for their deashed coals. At the same time, CO₂ is beneficial to the decomposition of organic sulfur at higher temperature. That the COS formation is related to CO at higher temperatures and has nothing to do with CO at lower temperatures is validated.