Abstract: According to the gas from the fire zone in the top small coal mine of the coal mining block directly threatened to the safety min-ing of the coal mining face, the air leakage source and converged features of the coal fire area in a Wuhai mine were analyzed. The analysis technology of the tracer gases was applied to determine the influence scope of the fire zone in small mine to the major coal mining faces and the connection relationship of the coal mining face. Then a physical model and boundary condition of the fire zone was established. The in-fluence time and migration law of CO in the fire zone to No.1604 coal mining block were simulated under the three statuses as the coal mining face not in the fire zone, the coal mining face under the fire zone and the coal mining face passed the fire zone. The results showedthat when the coal mining face was under the fire zone was not reached in the fire zone, CO concentration in the goaf would rise 30 minutes in advance than the coal mining face not in the fire zone, and in the air return flow of the coal mining face, CO risen value was higher thanthe air return corner. When the coal mining face passed the fire zone, CO concentration rose faster in the coal mining face and adjacent are-a. The simulation results were similar to the actual monitoring law of the fire zone. The study achievements could provide the theoretical basis to set up the mining planning and safety measures of the mining face.