The superfluous glycerol derived from biodiesel production can be a low-cost feedstock for hydrogen production via reforming technology. In this work, a La2O3 supported iridium catalyst was employed to catalyze the oxidative steam reforming of glycerol (OSRG) for hydrogen production, in the range of S/C ratio of 1-3,C/O ratio of 0.75-1 and 550-750 degrees C. The catalyst was modified with Na, Mg and Ca to optimize the catalytic performance in OSRG reaction. It was found that Ca is promising in promoting Ir/La2O3 catalyst for OSRG, offering excellent activity, hydrogen selectivity and stability. By combining multiple techniques, i.e. XRD, FTIR, Raman, XPS, H-2-TPR, CO2-TPD and HRTEM, the Ca modified Ir/La2O3 catalyst was characterized to understand the role of Ca promoter. Multi-functions of Ca were demonstrated, including inducing structural defects of La2O2CO3, endowing the catalyst strong basicity and tuning the metal-support interaction, which make the catalyst highly resistant to coking and sintering, therefore performing excellent long-term stability for 100 h. (C) 2012 Elsevier B.V. All rights reserved.