The invention discloses a printing and dyeing wastewater treatment method which comprises the following steps of: firstly mixing the printing and dyeing wastewater with domestic sewage; stirring at a certain pH value; and mixing intrinsic iron irons, magnesium ions, calcium ions and hydroxides of magnesium ions in the wastewater and the components such as suspended particles and the like in the domestic sewage to form a composite flocculating body with a synergistic effect. The composite flocculating body removes chromaticity in the printing and dyeing wastewater through the effects such as electrostatic adsorption, adhesion, bridging, sweeping and the like, and the domestic sewage is purified at the same time. The method disclosed by the invention is applicable to water-soluble and non-water soluble single kind or more kinds of mixed wastewater, and can be matched with a biological method or other physical and chemical methods for further treatment. The method has the characteristics of high decoloration degree, remarkable reduction of COD (chemical oxygen demand), suspended solids and total phosphorus and nitrogen, short treatment flow, simplicity in operation and management, only need for acid-base agents, low equipment investment and operation cost, no need of changing the original treatment facilities, wide application range, convenience in popularization and application and the like.