During the regeneration operation of whole helium purification train, helium purification system is depressurized to approximately 0.6 MPa. In the first operation phase, the closed loop for the regeneration of molecular sieve bed can be formed by isolating molecular sieve bed from helium purification system and collecting it to helium purification regeneration system, which mainly consists in sequence of diaphragm compressor, electric heater, molecular sieve bed of helium purification system, water cooler, water separator and auxiliary molecular sieve bed. Filled with helium from helium purification system, the closed loop operates at pressure of about 0.5–0.7 MPa. Driven by the diaphragm compressor, helium is heated by the electric heater and flows through the molecular sieve bed to desorb water at regeneration temperature of approximately 250–300 °C. The gas leaving the molecular sieve bed enters the water cooler of helium purification regeneration system where the cold water-cooled heat exchanger reduces gas temperature to approximately 10 °C. The water separator removes condensed water from the gas, and the residual water is adsorbed in the auxiliary molecular sieve bed. After the molecular sieve bed is regenerated at regeneration temperature of approximately 250–300 °C for several hours, the regeneration of molecular sieve bed ends. By the closed loop system for the regeneration of molecular sieve bed and its operation process, the tritium-containing waste water adsorbed in molecular sieve bed can be desorbed thoroughly, with a little part condensed in the water separator of helium purification regeneration system and most of part adsorbed in the auxiliary molecular sieve bed. When the regeneration of molecular sieve bed is finished, the molecular sieve bed is isolated from helium purification regeneration system.