In order to study the process of underground harmful gas CO dispersion into the refuge chamber and improve the survival rate of trapped personnel, a simple model of underground refuge chamber and main roadway was built. The influence of temperature and pressure air volume on CO dispersion in refuge chamber has been studied by analog experiment and numerical simulation, and the reliability of simulation results is verified. A flexible isolation door for controlling harmful gases in refuge chamber was designed, and the influence of the installation of the isolation door on CO dispersion has been compared and analyzed. The results show that when the temperature of the refuge chamber is lower than that of the harmful gas, CO will invade the refuge chamber from the upper part of the protective sealed door, and vice versa. The change stage of CO concentration in transition chamber can be divided into sudden drop stage, slow decline stage and unstable stage; The change stage of CO concentration in survival chamber can be divided into rapid decline stage and stable stage. When the temperature of the main roadway is 50°C and the temperature of the refuge chamber is 20°C, the pressure air volume within the safe range (24 ppm) of the CO concentration is reduced to 69.6% of that without the isolation door, effectively prevent harmful gases in the main alley from invading the refuge chamber.