Abstract: A promising method of on-line and real-time measurement for gas containing tritium in fuel processing systems of DT fusion facility was introduced. The principle of this method is observing the bremsstrahlung X-ray induced by the interaction between β particles and material (BIX). A correlation between the counting rate of bremsstrahlung X-ray and the tritium partial pressure can be presented, and it realizes the on-line and real-time monitoring of tritium partial pressure. The material used for generating bremsstrahlung X-rays is a beryllium window with evaporated golden film on it. The bremsstrahlung X-ray is monitored by a NaI(Tl) scintillation counter. For the pure tritium, when the tritium partial pressure range is 1 Pa-10 kPa (10¹²-10¹⁵ Bq/m³), the calibration curve of C-p is C=5.01×10⁴（1-e^-4.55×10-5p）. For the 1% atoms tritium mixture diluted with helium/hydrogen, when the tritium partial pressure range is 1 Pa-100 Pa (10¹¹-10¹⁴ Bq/m³), calibration curves of C-p are C=5.24×10² (1-e^-4.69×10-3p) and C=5.18×10²(1-e^-4.61×10-3p) respectively. The correlation coefficients of the three kinds of gases are 1.000 00, 0.998 60 and 0.999 53 respectively. Based on the above calibration curves, the expressions in random tritium partial pressure were tested. The results show that this method is good at measuring accuracy, responding rate and stability. It is a promising method in tritium measuring technique.