Hydrogen isotope permeation barriers (HIPB) have great potential applications in the fields of hydrogen energy and thermonuclear fusion energy. Here, we report the stability of Y2O3 HIPS in gaseous hydrogen at high temperatures including the structures, mechanical properties and electrical properties. With increasing hydrogen treatment time at 700 degrees C, the high-index diffractions of Y2O3 became weak gradually whereas the (400) diffraction was strengthened. The color of the Y2O3 HIPB changed from brown to gray. The bonding strength decreased by 61% with increasing hydrogen treatment time, and finally remained unchanged. Meanwhile, the electrical resistivity of the Y2O3 HIPB decreased from 8.2 x 10(9) Omega cm by over two orders of magnitude and then tended to be constant. The oxygen loss as well as hydrogen incorporation was proposed to be responsible for these modifications and indications of the present work for preparation of HIPB with high reliability were discussed. Copyright (c) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.