Based on the data and laboratory analysis of Sun-Cun Coal Mine, the relationship between the geothermal gradient and the depth of mine in Suncun Coal Mine has been developed. According to this and the laboratory experiments, the relationship between spontaneous combustion period of coal seam and the depth of the mine has been obtained in this article. The results show that the law of coal seam spontaneous combustion period and the mine depth in accordance with the relationship of the gauss curve expression and when the coal mine depth is around 1000 m, the coal seam spontaneous combustion period shortened dramatically. This law should be pay more attention to.

Basing on coal and the oxygen evolving complex theory, the method of study on the spontaneous combustion by analysis the microporous in coal has been established in this article. By the electron microscope, the process of microporous volume changeing with the temperature gradually increased is observed. It is believe that the process of spontaneous combustion reaction should be carried out in the microporous. Finally, under the help with finite element analysis , the temperature field surrounding microporous has been analyzed and the distribution regularity of the temperature field has been obtain. It make the conclusion that coal surface microporous can be used as evidence of coal spontaneous combustion reaction.