Abstract: The iron-sulfur compounds are produced easily in the process of oil and gas production by active sulfur and inactive sulfur with the iron. When exposed to air after a long period, it will result in spontaneous combustion, fire, explosion and other accidents. This paper describes the mechanism of iron-sulfur compounds formation and spontaneous combustion. The energy spectrum, X-ray diffraction and self thermal characteristic analysis are conducted for field samples. The conclusion shows that spontaneous combustion potential hazards of iron-sulfur compounds in Bohai oil and gas field are existed.