Active and tolerant Ni-based catalyst for methane steam reforming in direct internal reforming molten carbonate fuel cell (DIR-MCFC) was developed. Deactivation of reforming catalysts by alkalimetals from electrolyte composed of Li2CO3 and K2CO3 is one of the major obstacles to be overcome in commercialization of DIR-MCFC. Newly developed Ni/MgSiO3 reforming catalyst showed activities of ca. 82% methane conversion for 240 min in out-of-cell test. In duration test, the unit cell containing Ni foam impregnated with Ni/MgSiO3 in anode gas channel did not give performance degradation formore than 2000 h, while the unit cell assembled with Ni/MgSiO3-coated anode showed a significant performance loss after an operation of 1200 h. Results obtained from X-ray diffraction and Brunauer. Emmett.Teller technique revealed that Ni sintering and support deterioration were decisive factors in decreasing the catalytic activity.