A ship fire extinguishment and explosion suppression system comprises a particle trap, a desulfurizing and degassing device and a heat exchange device. The particle trap is connected with a ship exhaust gas collecting cover. Exhaust gas is subjected to primary cooling through the ship exhaust gas collecting cover. Particles in the ship exhaust gas are removed through the particle trap. The exhaustgas is deoxidized twice through the desulfurizing and degassing device, and meanwhile, sulfide, carbon monoxide and organic gas in the exhaust gas are removed. The exhaust gas is subjected to secondary cooling through a heat exchanger in the heat exchange device. The exhaust gas finally reaches to a shunt pipe through a buffer tank in the heat exchange device and then reaches fire extinguishmentnozzles to achieve fire extinguishment and explosion suppression. The ship fire extinguishment and explosion suppression system integrates the functions of ship exhaust gas treatment, preparation of agaseous extinguishing agent and seawater cooling and produces the nitrogen and carbon dioxide mixed gaseous extinguishing agent. The problems that the exhaust gas prepared extinguishing agent contains particles, oxygen, carbon monoxide and organic gas and is high in temperature are solved. Fast and high-efficiency totally-flooding inertion cooling on a whole ship is achieved.