Abstract: Through coal spontaneous combustion experiment and relation experiment between the particle size and the oxidation character of loose coal, some calculation formulae of characteristic parameters were obtained in the process of coal spontaneous combustion. According to these theories of porous medium hydrodynamics, mass transfer and heat transfer, the mathematical models of the air leak field, the oxygen concentration field and the temperature field were set up. By experimental and theoretical analysis a 3-D dynamic mathematical model of coal spontaneous combustion was proposed, the method of ascertaining the boundary condition of the model was analyzed, and the finite difference method was adopted to solve the 2-D mathematical model.