The invention discloses a tri-
cogeneration system and a tri-
cogeneration method for generating power, producing 
hydrogen and producing 
fresh water by the aid of a high-temperature gas-cooled reactor of a 
nuclear power plant. The tri-
cogeneration system comprises a closed 
helium circulating 
system of the 
nuclear power plant, a 
superheater, a steam generator, a raw 
seawater pipeline, a flash 
evaporator, a steam ejector, a 
seawater desalting device, a water feeding pump, a 
solid oxide electrolytic tank and an auxiliary steam pipeline. The tri-cogeneration system and the tri-cogeneration method have the advantages that the circulating system of the 
nuclear power plant, steam 
electrolysis and 
hydrogen production processes and 
distillation seawater desalination processes are coupled with one another, the power is generated by the aid of a 
helium gas 
turbine at first, 
waste heat of partial 
exhaust gas of the 
helium gas 
turbine is used for electrolyzing steam and producing the 
hydrogen, low-temperature 
waste heat cooling water of a cooler is used for carrying out 
distillation seawater desalination by means of coupled 
flash evaporation and 
steam injection, and accordingly diversified water, power and hydrogen tri-cogeneration 
modes can be implemented; the 
electric power and the 
fresh water which are required for steam 
electrolysis and 
hydrogen production can be provided by means of 
seawater desalination and nuclear power generation, accordingly, the tri-cogeneration system is high in circulating heat efficiency and good in adjustment performance and has a good economic benefit, the reliability of equipment can be improved, environmental 
pollution can be reduced, the tri-cogeneration system and the tri-cogeneration method have excellent application prospects, and the like.