Reclaimed water is suitable for the deep treatment of low concentration fluorine-containing wastewater. Fluoride ions in the solution are separated by sieving through a semi permeable membrane under different pressure differentials and external forces, effectively intercepting fluoride ions and other small molecule pollutants, and producing high-quality recycled water. The double membrane method can convert about 75% of low fluoride wastewater into regenerated water, and 25% of reverse osmosis concentrated water enters the FBC calcium fluoride crystallization system for treatment.