NOVELTY - Cold rolling leveling liquid wastewater is treated by conveying wastewater to adjusting tank to reduce chemical oxygen demand (COD) concentration and oil content of wastewater; conveying wastewater to coagulation reaction tank to absorb suspended particles; conveying wastewater to cavitation air floatation (CAF) tank to produce air flotation and remove solid pollutant in wastewater; performing anaerobic treatment to wastewater to convert organic pollutant into biogas; and treating using membrane bioreaction (MBR) unit to convert residual organic pollutant into carbon dioxide (CO2) and water.    USE - Method of treating cold rolling leveling liquid wastewater (claimed).    ADVANTAGE - The method requires small investment, less space, and low operation cost. The anaerobic treatment and the MBR bioreaction treatment can avoid temperature problem, overload problem, and shock load problem in aerobic treatment, to ensure that the aerobic water reaches the standard. The organic density in water is reduced to less than 100 mg/L COD. Hence, the quality of treated water conforms to first level standard of GB8978-1996.    DETAILED DESCRIPTION - Treatment of cold rolling leveling liquid wastewater comprises:    (A) conveying wastewater to an adjusting tank for oil collection treatment to reduce COD concentration and oil content of wastewater;    (B) conveying the wastewater to a coagulation reaction tank for coagulation reaction and absorption of the suspended particles in the wastewater to form air flotation;    (C) conveying the wastewater after coagulation reaction to CAF tank to produce air flotation and remove the solid pollutant in the wastewater through CAF air flotation way;    (D) treating the wastewater using anaerobic treatment to convert the organic pollutant into biogas, and then treating using MBR unit to convert the residual organic pollutant into carbon dioxide (CO2) and water; and    (E) discharging or recovering the water.    An INDEPENDENT CLAIM is included for a wastewater treatment device of cold rolling leveling liquid, comprising an adjusting tank; a coagulating reaction tank; a CAF tank; an anaerobic treatment unit; and an MBR unit.