Abstract: Through the analysis about nature ventilation system characters and the air-flow movement laws in coalfield outcrop fire area, the basic equations of coalfield outcrop fire area are obtained. The coalfield outcrop fire areas in the case of different parameters are simulated by Fluent software. The results show that the temperature of the burning gas in the process of seepage flow is basically identical with the temperature of the environment; the gas temperature rapidly rises and reaches a peak after going through the burning area, and it produces larger fire pressure. The combined action from fire pressure and nature pressure provides fire ventilation. On the route of getting across the burning area, the movement of the gas conforms to the law of conservation of energy, Darcy's law (inlet air lines) and narrow gap fluid motion law of Boussines. On the route of air leakage, the gas moves according to the Laws of conservation of energy and Darcy's law.