The invention relates to a method for treating printing and dyeing wastewater by a composite biological enzyme. The method comprises the following technological steps: 1), pumping the printing and dyeing wastewater into a regulating tank and keeping the printing and dyeing wastewater in the regulating tank for 10.5 hours; 2), conveying the wastewater into a primary settling tank, adding FeSO4 and liquid caustic soda, and keeping the wastewater in the primary settling tank for 7.25 hours; 3), conveying the wastewater into an anaerobic tank, adding an anaerase and a coenzyme, and keeping the wastewater in the anaerobic tank for 14.9 hours; 4), conveying the wastewater into a medium settling tank and keeping the wastewater in the medium settling tank for 16.56 hours; 5), conveying the wastewater into an aeration tank, adding an aerobiotic enzyme and a coenzyme, introducing air to aerate, and keeping the wastewater in the aeration tank for 37.4 hours; and 6), conveying the wastewater into a final settling tank, and discharging the effluent after mud and water are separated in the final settling tank. The method for treating the printing and dyeing wastewater by the composite biological enzyme has the advantages of good treatment effect, low cost, and reduction of secondary pollution, etc.