When compartment fire reaches flashover, the temperature rises rapidly, resulting in the ignition of all surfaces of the combustibles within the compartment. In this paper, the suppression method of adding sand into the fire source (gasoline) is discussed. Through assuminga transition layer below the surface of sand, the combustion process of the fire source can be simplified. It is found that the time to the peak value of the upper layer temperature, the peak value itself and the rate of extinguishment have obvious dependence on the volume ratio of sand to the fire source (gasoline) . Experimental results show that the theoretical analy is reasonable.