Abstract: The two separation materials Pd/K and Pd/Al₂O₃ used in thermal cycling absorption process for hydrogen isotopes separation were investigated and compared. The contents of palladium in Pd/K and Pd/Al₂O₃ measured by means of X-ray fluorescence analyzer are (40.8±0.1)% and (45.3±0.1)%, respectively. The morphological characters and X-ray diffraction patterns of these two materials were respectively recorded with SEM and XRD, compared and discussed. The saturated absorption capacities of hydrogen stored by Pd/K and Pd/Al₂O₃ are 73.12 mL/g(STP) and 70.98 mL/g(STP), respectively. The separation experiments of H-D were studied via TCAP using 901.7 g Pd/K and 1.558 g Pd/Al₂O₃, respectively. The results show that the Pd/Al₂O₃ is better than Pd/K in separating hydrogen isotopes.