Abstract: With the development of nuclear industry technology, the use of nuclear fuel is gradually increasing and the amount of produced spent fuel is increasing. During the reprocessing process of spent fuel, a large amount of low concentration tritium-containing purified water is generated. China’s backup spent fuel reprocessing plants are established in inland areas and use air carrying emission technology with certain shortcomings such as limited increase in air carrying capacity, and the air after carrying may experience re-condensation due to temperature and humidity imbalance, resulting in environmental pollution. In response to the low emission efficiency and poor environmental adaptability of the existing tritium-containing purified water air carrier technology, which could not effectively meet the practical needs of spent fuel reprocessing development, a two-step air carrier tritium-containing purified water system was proposed in this paper based on LiBr refrigeration drive solution dehumidification and efficient humidification. A prototype of the two-step tritium-containing purified water air carrier system was established with carrier capacity larger than 2 t/d, and its operational characteristics under different conditions were systematically studied based on the criteria of safety and efficient discharge. The results show that no condensation phenomenon occurs at the outlet of the carrier air, indicating that the experimental prototype is able to safely and efficiently discharge tritium-containing purified water under environmental conditions of air temperature ranging from 3 ℃ to 50 ℃ and air relative humidity ranging from 0 to 90%. Under the standard condition with an air temperature of 22 ℃ and air relative humidity of 47%, the carrier capacity of the experimental prototype is 100.8 kg/h, which is 298.4% higher than the one-step method. Under the high relative humidity condition with an air temperature of 25 ℃ and air relative humidity of 90%, the carrier capacity of the experimental prototype is 119.9 kg/h, which is 508.6% higher than the one-step method. Under the low temperature condition with an air temperature of 3 ℃ and air relative humidity of 70%, the carrier capacity of the experimental prototype is 17.4 kg/h. Under the high temperature condition with an air temperature of 50 ℃ and air relative humidity of 20%, the carrier capacity of the experimental prototype is 96.0 kg/h, which is 60.0% higher than the one-step method. The above results indicate that the two-step method can significantly expand the environmental adaptation range for safe discharge of tritium-containing purified water, and the emission efficiency is high. The results in this paper can provide reference for the application of tritium-containing purified water discharge.