The online tritium production irradiation loop in the thermal neutron reactor is designed in order to satisfy the demands of the fusion energy research. A tritium production and release loop can be used to evaluate the breeding material irradiation and to study the tritium carrier and the cycle parameters. This paper presents a review of the main process systems and the core components of CITP-Ⅱ. The irradiation capsule is for the safety irradiation of the breeding material in the pile; the carrier gas system is for the online reload and release of the tritium; the gap gas and purification system is to control the breeding material temperature and the tritium release temperature window; the theoretical calculations and the determined loop operation parameters can provide some guidance for the CITP-Ⅱ operation and the tritium production and release research.