Abstract: The types of sulfur and its variation of content in coal samples of different densities are investigated using XPS. Result of study shows that: the low-density coal samples have only negligible content of inorganic sulfur which tends to increase with the increase of coal density; the organic sulfur is mainly in the forms of mercaptan sulfur, thiophenic sulfur and sulfoxide sulfur and among then, the mercaptan sulfur helds the lion′s share, followed by thiophenic and sulfoxide sulfur; and with the increase of coal density, the organic sulfur shows largely a declining tendency. Though the research-derived accomplishments, a belter insight into the types and structure of sulfur contained in coal can be gained for improving microwave desulfurization efficiency.