Catalytic activities of pellet-shape Ni-Fe/MgO-Al2O3 with and without Gd-CeO2 (CGO) coating toward steam reforming of naphthalene (as tar model compound) and biomass tar from pyrolysis of eucalyptus in the presence of H2S was studied under various conditions including different temperatures (between 700 and 900 degrees C), inlet H2S (from 100 to 1000 ppm) and inlet H2O concentrations. It was found that under sufficient conditions CGO coating can efficiently promote sulfur tolerant and resistance toward carbon deposition of Ni-Fe/MgO-Al2O3, from which less deactivation occurs after prolong testing (18 h) compared to the catalyst without CGO coating. In addition, the catalyst activity can be completely regenerated by purging air at 800 degrees C, from which almost the same level of H-2 yield can be enhanced after regeneration. It was revealed from the study that in the presence of sufficient H2O concentration, the phase of CeO2 potentially transforms to Ce(SO4)(2), which helps Ni-Fe/MgO-Al2O3 promote high tar reforming activity. In contrast, with less H2O presenting, Ce2O2S is formed and consequently results in low sulfur tolerant activity. Nevertheless, by purging Ce2O2S with air, the phases of CeO2 and Ce(SO4)(2) can be effectively recovered. This study therefore highlights the great benefit of CGO coating over Ni-Fe/MgO -Al2O3 for tar reforming in terms of sulphur tolerant promotion and achievable catalyst regeneration. (C) 2014 Elsevier B.V. All rights reserved.