Abstract The combustion process of the organically bound tritium (OBT) analysis method is difficult and requires sophisticated techniques. For ease, safety, and reproducibility a semi-automatic combustion system was developed. An arbitrary combustion program that prevents sudden ignition was devised and combustion tests were conducted. Analytical test runs were conducted using fish standard samples to confirm the validity of the developed system. The test values were compared with values obtained with another analysis method, and the recovery rate of the combustion water was evaluated. The results confirmed that the analytical values obtained with this combustion system were equivalent to those obtained with another analytical method and were valid for OBT analysis.