The invention relates to a method for recycling calcium and magnesium ions in desulfurization wastewater by a lime milk method, and belongs to comprehensive recycling and utilization of wastewater inthe technical field of environmental protection. According to the method, in accordance with the characteristics of high concentration of calcium and magnesium ions and sulfate ions in desulfurizationwastewater of a power plant, the calcium and magnesium ions are separated by adding the lime milk in the desulfurization wastewater of the power plant, and then through recycling, a slurry magnesiumhydroxide product and calcium sulfate and sodium chloride by-products are prepared. According to the method, not only is emission reduction of the wastewater achieved, but also the wastewater is subjected to resource utilization.