Abstract: Gas overrun is the direct reason of gas accident in coal mine. This article took Dafosi Mine as an example to analyze the causes of gas overrun in the coal mine, introduced a series of targeted measures for gas prevention. By using the prevention measures including enhancing management of mine ventilation, taking comprehensive means of gas drainage, strengthening the gas monitoring and control at particular location and time, configuring safe standby power and enhancing safety management, Dafosi Mine gas emission quantity was significantly reduced and the times of gas overrun were reduced from 12 to 0. Through these processes, we effectively eliminate the phenomenon of gas overrun and ensured the safety of mining.