Abstract: The differences between the thermal conductivities of helium gas and hydrogen isotope gas are very small. Applying zirconia primary battery as the detector of gas chromatography and modified γ-Al₂O₃ as the filled column, the influencing factors of the measurement of hydrogen isotopes by zirconia detector were studied systemically at liquid nitrogen temperature (77 K). The separation test of trace hydrogen isotopes in the helium gas was also performed. The results show that the optimal working temperature of zirconia detector is about 700 ℃. Under the condition that the flow rate of the purge gas is 60 mL/min, the relative standard deviation of the instrument measurement is smaller than 1%, the detection limits of H₂ and D₂ are 15 ppm and 40 ppm, respectively, and the relative error is smaller than 5%. The above results indicate that zirconia detector can be used for the measurement of trace hydrogen isotopes in helium gas.