Water mists for fire suppression and control have widely received considerable attention as one of the potential methods for halon replacement. A new composite additive was concocted and its effectiveness to water mist's fire suppression performance was investigated through the base of ethanol fire, diesel fire and wood crib fire. Results showed that this additive can greatly improve the fire suppression efficiency of water mist and shorten the extinguishing time remarkably. The fire suppression mechanism of water mist with this additive was combined with physical and chemical effect. However, the surface cooling and fuel isolation were considered to be the crucial suppression mechanism.