A method for treating industrial wastewater in the field of wastewater treatment technology. It involves diverting wastewater to a collection pond, adjusting the pH of the last compartment in the pond, using a primary dissolved air pump to elevate the water to a primary pressure dissolved air tank, while simultaneously introducing air and coagulant dyeing agents. The saturated dissolved air water at primary pressure is then abruptly released into a primary air flotation tank to form primary treated water; the overflow of the primary treated water into a buffer pond, followed by lifting it to the secondary pressure dissolved air tank using a secondary dissolved air pump while introducing air and coagulant dyeing agents. The saturated dissolved air water at secondary pressure is then abruptly released into a secondary air flotation tank to form secondary treated water, which overflows into a sedimentation pond for sedimentation before being discharged. Sludge from the first and second air flotation tanks is transferred to a sludge pond, filtered into filter cakes, and the filtrate is recycled back to the collection pond. The removal rates of CODcr, decolorization rate, SS, and BOD5 in the treated industrial wastewater are 80-90%, 95%, over 90%, and 75-80% respectively, meeting the GB8978-1996 first-grade water discharge standards. Biogas power generation is a new comprehensive energy utilization technology integrating environmental protection and energy conservation. It utilizes biogas produced from anaerobic fermentation of industrial wastewater to drive biogas power generation units for electricity generation, and can make full use of the excess heat from the power generation units for biogas production, achieving a comprehensive thermal efficiency of around 80%, significantly higher than the general power generation efficiency of 30-40%. This method is an excellent way to treat industrial wastewater.