Abstract: That disordered characteristics and its disaster evolution characteristics of mine ventilation system caused by as⁃censional airflow fire is a focus of mine fire research. Through repeated experiments，the variation laws of tem⁃ perature and air volume in main and side branches of ventilation system with different ventilation capacity due to as⁃ censional airflow fire are obtained. Using the TF1M(3D)，a catastrophic ventilation simulation software，to solve the problems of mine physical ventilation，combined with the analysis on the example，the variation of ascensional airflow fire and the process of disordered ventilation system in the whole mine are described in detail. It is shown that in the mine ventilation system，the combustion plays a role of the power source of non⁃controlled energy release，and its fire pressure interacts with the thermal resistance of mine ventilation，which directly causes the airflow disorder of the mine ventilation system. As the fire intensifies， the ascensional airflow fire can cause the airflow in side branch to decrease，stagnate or even reverse，which may lead to the expansion of the disaster and seriously affect the speed of disaster relief. Improving the fan supply capacity can not only reduce the ventilation thermal resistance in⁃ crement of the side branch，but also avoid the airflow reversal of the side branch at the same time. The simulation re⁃ sultsusing the software TF1M3D demonstrate that when the speed of mine fan increases from 540 r/min to 740 r / min，the reversal of smoke flow in the side branch ( the 402 working face) caused by ascensional airflow fire is overcome. In terms of variation law，the theoretical results and the experimental results are mutually verified.