Using Mossbauer and X-ray Photoelectron Spectroscopy (XPS) techniques the sulfur forms in solid products obtained at different reaction were analyzed. The results show that: during supercritical desulfurization the pyritic sulfur is removed as following process: FeS2-->FeS+Fe1-xS, the transformation amounts and the value of x are dependent on reaction conditions, especially on temperature. The conversion of pyrite is very little at 275 degrees C. Pyrrhotite (Fe1-xS) is FeS1.101 at 275 degrees C and FeS1.085 at 450 degrees C. Among the organic sulfur groups PhSH. Ph(2)S and thiolane are easily removed; Ph(2)SO is more difficult to be removed, its removal may be realized by increasing temperature and adding some water into ethanol; thiophene is most difficult to be removed, its removal needs high reaction temperature.