The correlation between oxygen concentration and fire temperature when fire was extinguished with water mist was theoretically studied. The Semenov theory was applied to analyze the critical condition when fire was extinguished with water mist, from which the correlation could be obtained. The water mist experiments were carried out by varying the fire size, atomizer number, ceiling height, system pressure, and pre-burn time in an enclosed room. The oxygen concentration near the edge of the liquid pool and the fire temperature above the center of the liquid pool were measured. A comparison of the experimental data with the correlation was made under different conditions. The results showed that fire extinguishment was a stochastic process which could be affected by many factors. This theoretical model could predict the correlation between fire temperature and oxygen concentration when fire was extinguished with water mist in an enclosed room and it can also be treated as a critical condition for fire extinguishment. The correlation between oxygen concentration and fire Temperature when fire was extinguished with water mist was theoretically studied. The Semenov theory was applied to analyze the critical condition when fire was extinguished with water mist, from the the correlation could be. The water mist trials were carried out by varying the fire size, atomizer number, ceiling height, system pressure, and pre-burn time in an enclosed room. The oxygen concentration near the edge of the liquid pool and the fire temperature above the center of the liquid pool were measured A comparison of the experimental data with the correlation was made under different conditions. The results showed that fire extinguishment was a stochastic process which could be affected by many factors. This theoretical model could predict the correlation between fire temperature and oxygen concentration when fire was extinguished with water mist in an enclosed room and it can also be treated as a critical con dition for fire extinguishment.