Coalfield fire is prevalent in the world. especially in China, but the main reason of the fire in the coalfield is not clarity. So it\'s difficult to fight the coalfield fire. Based on the model of outcrop spontaneous combustion in coalfield, that when the fringe coal-rock is break up by the alternation air-temperature, the coal is oxygenated and heat is emitted. Then around coal-rock is heated and break up. The air-leakage conditions are changed and the convection of air in the coal-rock is come into being. The self-ignition process of fringe coal-crock is developed to the deeper coal seam. The oxidation and emitting heat mechanics process of coal, breakage and air-leakage mechanics process of the coal-rock in the coalfield are theoretically analyzed.