Abstract: Experimental study was carried out on the fire extinguishing characteristics of water mist in the simulation tunnel by building the fire extinguising test platform of the simulation tunnel and the generation device of the water mist and using the variable control method, and analysis was made on its influence factors. The experiments showed that the water mist can effectively and rapidly extinguish the fire in the simulation tunnel and its fire extinguishing effect was obvious. The zise of water mist, the air velocity in the simulation tunnel, the inclination angle and ventilation mode of the simulation tunnel have some influence on the water mist in suppressing and extinguishing the simulated fire source.