A compact tritium detector using inorganic fluorescent powders has been developed to measure the partial pressure of tritium in a deuterium-tritium mixture. The inside of the tritium detector was filled with the fluorescent powder which was optically coupled to a photon counter. Various fluorescent powders were evaluated in terms of sensitivity, linearity, signal-to-noise ratio and radiation damage. Within the measurement accuracy of ± 3%, intensity of fluorescence emitted from each fluorescent powder was completely proportional to the total DT gas pressure ranging from 0.07 atm to 7 atm and also to the tritium concentration in the mixture.