Abstract: A method for treating wastewater including: flocculating and granulating the wastewater in a wastewater collection pool through a flocculation sedimentation tank; pumping the flocculated water with a high/low turbidity into a hair filter through a lift pump; pumping the pretreated water into an organic/inorganic membrane filter to yield clear water containing detergent; treating the clear water containing detergent with activated carbon and an ultraviolet lamp; raising the water pressure to 10-15 Kg using a high-pressure pump, and pumping the neutral clear water into a reverse osmosis apparatus for further removal of inorganic matters, organic matters, virus, and bacteria to obtain purified water. A device for recycling treatment of car-washing and laundry wastewater is also provided.