Calcium and magnesium elements were separated from alkali residue by calcining reaction,digestion reaction,ammonium chloride leaching reaction,CO₂ carbonization reaction,decomposition reaction and other technological steps,andthree products with high purity of 99.9% light calcium carbonate,98.9% magnesium carbonate and insoluble neutral residue were obtained respectively with alkali residue and CO₂ as the main raw materials.The new technology enables the comprehen-sive utilization of alkali residue,the recycling of mother liquor and the zero discharge of three wastes,which is undoubtedly a new breakthrough in the comprehensive utilization of alkali residue.Its main raw material cost is zero,the main cost is water,electricity,fuel,equipment depreciation,labor wages and a small number of additives,etc.,can be expected to have good environmental benefits,social benefits and economic benefits.Once it realizes the industrialization,combining with the utilization of the patent technology of steam ammonia waste liquid resources,it will become a key to break the shackles and bottleneck of the sustainable development of ammonia alkali plant.