Abstract: Aimed at the problem of gas explosion in coal mine after sealing the fire zone, experiments were conducted to analyze the impact factors of gas explosion limits including temperature, pressure, combustible gas (CO) and inert gas (N2 and CO2). The experimental results show that at normal temperature and pressure, the lower gas explosion limit is at the methane volume fraction of 5 percent and the upper gas explosion limit is at the methane volume fraction of 13.5 percent. And CO2 has greater inerting effect than N2. According to the experimental data, a new explosion triangle of mixed inflammable gases is rebuilt and the inerting regions were newly divided, which can provide a new method to prevent gas explosion after sealing the fire region. Amount of inert gas which needed to ensure against explosion can be calculated by the explosion triangle. Meanwhile, properly controlling the impact factors can decrease the risk of gas explosion.