The invention discloses a complete recycle-enhanced separation technology, CREST for short, and belongs to the field of treatment of desulfurization wastewater in thermal power plants and treatment of industrial wastewater in other industries. The technology specifically includes the first step of extraction of crystal magnesium hydroxide, the second step of extraction of calcium sulfate, the third step of enrichment of boron ions and the fourth step of purification of a sodium chloride solution. According to the deep graded salt separation technology, flue gas desulfurization wastewater in thermal power plants is completely recycled for the first time, no new wastewater or solid waste will be generated after treatment with the system, and a real sense of zero emission and recycle can be achieved, so that the technology has extremely huge market demands and benefits.