The invention discloses a transcritical air conditioner and seawater desalination co-production system which comprises a transcritical air conditioner with a refrigerating cycling unit and a low-temperature multi-effect distillation apparatus. The low-temperature multi-effect distillation apparatus comprises a multi-effect distillation unit, a fresh water collection pipeline used for collecting liquid fresh water and a concentrated wastewater external draining pipe used for collecting tail end concentrated seawater, an air cooler of the refrigerating cycling unit is divided into two or more sections in the flow direction of a refrigerating agent, and from a first-effect distillation unit body, all sections of the air cooler are sequentially connected into corresponding effect distillation unit bodies to serve as air-cooling modules. By means of the transcritical air conditioner and seawater desalination co-production system, the use ratio of the low-temperature multi-effect distillation apparatus on the exhaust heat generated by the transcritical air conditioner and the fresh water yield of the low-temperature multi-effect distillation apparatus are increased, and the air cooler of the transcritical air conditioner is directly installed inside distillation unit bodies of all effects, so that the whole system is more compact, and the whole size is reduced.