Various methods of tritium measurement have been applied depending on a chemical form of tritium. A method combined oxidation catalyst and water bubblers has been used as one of the most quantitative analysis methods for gaseous tritium. The major technical shortcoming with the conventional methods is the lowering of quantitative accuracy caused by adsorption of produced tritiated vapor on hydrophilic oxidation catalyst. Then, we developed an organic-based hydrophobic platinum catalyst. The catalyst enhanced its hydrophobicity to prevent absorption of water vapor on catalyst surface. In order to ensure to oxidize tritium, we additionally devised 1) the particle size of the catalyst made small to be around 1mmϕ and 2) intentional addition of hydrogen. As the result of experimental verification of the proposed method, we succeeded to achieve the high accuracy of more than 99.9% in the quantitative measurement of tritium. The developed tritium measurement system is applicable widely for various tritium measurements, estimation of tritium generation rate at TBM, tritium behavior in various materials and so on.