The invention relates to a method for improving AAO treated dyeing wastewater and a device thereof. The device comprises an anaerobic reactor, a primary settling tank, an anoxic reactor, an aerobic reactor and a secondary settling tank, wherein the anaerobic reactor is communicated with the primary settling tank, the anoxic reactor, the aerobic reactor and the secondary settling tank through pipelines in sequence; the primary settling tank is communicated with the anaerobic reactor through a sludge pump by a return pipe; the aerobic reactor is communicated with the anoxic reactor through the sludge pump by the return pipe; and the secondary settling tank is communicated with the aerobic reactor through the sludge pump by the return pipe. The method comprises the following steps: controlling the reflux ratio of sludge to be maintained at 100 percent and the reflux ratio of mixed solution to be 100 percent without sludge discharge at environmental temperature of between 20 and 30 DEG C, wherein preferably, retention period of an anaerobic unit is 6.5 hours, retention period of an anoxic unit is 6.5 hours, and the retention period of an anoxic unit is 16 hours; and then discharging water. The method and the device are organically combined with anaerobic, anoxic and aerobic biological treatment methods to achieve advantage complementation with one another.