TiVCr alloys are treated as candidate materials for hydrogen isotope separation because of their prominent inverse isotope effects and hydrogen storage properties. In this work, the relationship between the separation factor (alpha(H-D)) that characterizes the isotope effects and the ratio of equilibrium pressures (R-P) of the isotopes was investigated. It was found that alpha(H-D) in the plateau region was independent on R-P of the alpha-phase if the phase transitions during hydrogenating are merely dependent on the hydrogen content and not on the type of hydrogen isotopes. In order to deal with the gradient plateau region that originates from the inhomogeneous compositions of TiVCr alloys, a model relating alpha(H-D) in the single gamma-phase to R-P in the gradient plateau region was formulated. Furthermore, the values of alpha(H-D) were also determined by experiments for Ti0.3V0.4Cr0.3-hydrogen systems, and compared with the prediction results, providing validations to the formulated model. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.