The invention relates to a tritium-containing wastewater treatment system and treatment method. The system is formed by cascading multiple stages of water rectifying towers and then being cascaded with a single-stage N-VPCE, tritium-containing wastewater is pretreated with the multi-stage water rectifying tower cascading system and rectified into a low-tritium-content component and multiple high-tritium-content components of which the tritium concentrations are gradually increased; an N-VPCE column steam-phase catalytic exchange is introduced into the high-tritium-content components of which the tritium concentrations are gradually increased from the bottom to top in the state of high-temperature steam according to the tritium concentration sequence from low to high, hydrogen is introduced from the bottom of the N-VPCE column steam-phase catalytic exchange, tritium in the steam is transferred into the hydrogen phase through catalytic exchange, and water flowing out of N-VPCE column steam-phase catalytic exchange is fed back to the last-stage rectifying tower. The tritium-containing wastewater treatment system is simple in structure, reasonable in procedure and low in construction and operation cost; the treatment method is high in practicability and stable and reliable in operation, can be used for solving the technical problem of inland nuclear power tritium environment emission control and is suitable for tritium-poor water production.