The invention provides a system for separating an ammonia and carbon dioxide mixed gas, comprises the following steps of: firstly, compressing the ammonia and carbon dioxide mixed gas, transmitting into a carbon dioxide separation tower after the pressure is increased to 15-25bar, and sequentially entering into a water separation tower and an ammonia separation tower. The system has the advantages that the electric energy consumed by compressing the tail gas is converted into the enthalpy of the tail gas, a great quantity of the released heat energy can be effectively used when the ammonia in the tail gas is absorbed by a carbon separation tower; and the system can isolate the dilute ammonia carbon water solution from the side line of the water separation tower, so that the load of the water separation tower can be greatly reduced, and the energy consumption can be reduced. Furthermore, the mixed gas is further compressed into a plurality of segments, and the intersegment cooling adopts a direct spray liquid cooling method, rather than an unconventional indirect water cooling method, so that the system has the advantages that the sensible heat is converted into the latent heat, however, the total enthalpy value of the logistics can be invariably kept. The fourth advantage of the system is to replace a cooler taking circulating cooling water as a cooling medium with an air cooler, so that the energy consumption can be reduced.