The invention provides an LNG cold energy seawater desalination and concentrated saltwater comprehensive utilization technology. The technology comprises the following steps: taking seawater/industrial wastewater, which contains sodium chloride, magnesium sulfate, calcium sulfate, potassium chloride, sodium bromide, and magnesium chloride, as the raw material, carrying out a desalination treatment to obtain fresh water and concentrated saltwater; preparing bromine and de-brominated concentrated saltwater from concentrated saltwater through an air blowing method; adding caustic soda and sodium carbonate into de-brominated concentrated saltwater to produce magnesium hydroxide, calcium carbonate, and refined bittern; freezing refined bittern by LNG cold energy to produce sodium sulfate decahydrate and desulfurized mother liquor at a freezing temperature of -4 to -30 DEG C; subjecting the desulfurized mother liquor to high temperature evaporation at a temperature of 90 to 150 DEG C to produce sodium chloride and salt making mother liquor, delivering the sodium chloride to offshore caisson for creating marine reclamation land, subjecting the salt making mother liquor to low temperature evaporation at a temperature of 20 to 60 DEG C so as to produce potassium chloride and potassium salt mother liquor, and returning the potassium salt mother liquor to the refined bittern. The procedure and cold energy are reasonably utilized, the additional value of product is increased, the production cost and energy consumption are low, and the technology can be used to desalinate seawater in a large scale.