By introducing the theory of system safety science, and applying the gray theory prediction method, this paper aims at analysing the major hazards of spontaneous combustion of coal, and divided the impact indicators system into three categories, namely; static indicator, dynamic indicator, and intensive monitoring indicator. The static class indicator determined the hazard class by using risk evaluation, and obtained the inherent hazard class of hazard source. The dynamic class indicator serves as a real-time monitoring item. After analysing the monitoring result by the gray theory prediction, both the monitoring result and inherent hazard class were jointly integrated into the initial hazard class. After the initial hazard class was amended by intensive monitoring indicator, it became possible to obtain the ultimate hazard class corresponding to the major hazards of spontaneous combustion of coal. In the early warning of Coal Mine Gas and the major hazard of fire disaster, it was proposed to adopt the combination of dynamic and static early warning method. In essence, the static early warning serves as a kind of “early warning” for the current state of early warning indicator, while the dynamic early warning serves as the predictive judgment about the current state of early warning indicator, based on the analysis of the development trends.