Ni-supported catalysts on perovskite-type oxides have been prepared by “solid phase crystallization” ( spc) method and tested for CO 2 reforming of CH 4 into synthesis gas at 850°C. The Ni catalysts were obtained in situ during the reaction from the oxides as the precursors in which nickel species were homogeneously incorporated in the perovskite structure. Ni/Ca 0.8Sr 0.2TiO 3 and Ni/BaTiO 3 catalysts showed high activity as well as high sustainability among the catalysts tested. The high activity may be due to highly dispersed and stable Ni metal particles (diameter<1 nm) on the perovskite, where the nickel species thermally evolve from the cations homogeneously distributed in an inert perovskite matrix as the precursors during the reaction. Nickel species was partly incorporated in the perovskite structure by replacing the Ti site and partly separated as NiO from the structure after the calcination of the precursors, and the former species likely affords the highly dispersed Ni metal under the reducing atmosphere. The amount of NiO detected by XRD analyses was smaller on BaTiO 3 than on Ca 0.8Sr 0.2TiO 3, while that of surface Ni obtained by TGA was larger on Ca 0.8Sr 0.2TiO 3 than on BaTiO 3. It is thus likely that an incorporation of Ni was enhanced in BaTiO 3 compared to Ca 0.8Sr 0.2TiO 3, resulting in the higher dispersion of Ni metal particles on the former support. This well coincided with the activity of Ni/BaTiO 3 being higher than that of Ni/Ca 0.8Sr 0.2TiO 3 at high space velocity. The high sustainability against coke formation may be partly due to the mobile oxygen as well as due to the presence of alkaline earth metals in the perovskite supports. Oxygen mobility in the perovskite was further tested by CO 2 pulse reactions, suggesting an easy migration of oxygen over the perovskite structure. It is most likely that the oxygen easily migrates from the supports to the surface of fine Ni particles, where the coke material can be oxidized into carbon oxides.