The displacement chromatography technique with a tri-column system was used to reduce the protium (H) in the deuterium-tritium (D-T) mixture, and the separation performance was studied numerically by ANSYS FLUENT. The experimental results showed that the isotopic abundance of H in the D-T mixture dropped from 2.7% to an acceptable level of 0.88%. The simulation results showed that a lower porosity (theta) of the filling material made a higher separation factor, but a lower separation efficiency. The velocity of the product gas at the outlet of the separation column approximately had a linear relationship with theta(5/3)/(1-theta)(2), which partly indicated the pore diffusion resistance. The mixed gas could contact the filling materials more sufficiently under a lower flow rate resulting in a lower protium concentration in the product gas. The separation column with a thin and long shape had a better separation performance and a lower product gas loss. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.