Abstract: The analysis technology for the ion-chamber is used to measure the tritium concentration in heavy water reactor power plants. However, the online tritium-in-air monitoring system cannot measure tritium from multiple areas continuously. The system extraction technology has been modified to improve the system reliability. The modification results indicate that the system obtains accurate and real-time measurement readings, and that it can provide very important evidence for the locating of tritium leakage and the radiation protection of operators in nuclear power plants.