One of the important developments in CO2 reforming of methane is highly effective MgO-based solid-solution catalysts. Herein, their high activity and selectivity as well as excellent stability for CO2 reforming of methane were briefly reviewed. How to inhibit carbon deposition via the formation of NiOMgO or CoO-MgO solid solution was discussed. The reduction of NiO (or Coo) in the NiO-MgO (or CoO-MgO) solid solution is much more difficult than that of pure NiO (or CoO), which contributes to the formation of very small Ni particles to inhibit carbon deposition. It is generally recognized that the reduction of a metal oxide is determined by its metal-oxygen bond strength. Herein, however, it was showed that the reduction of a metal oxide is strongly dependent oil both metal-oxygen bond strength of the metal oxide and the metal-metal bond strength of its metal product. Furthermore, it was proposed that a critical factor to control the reduction of NiO (or CoO) in the solid solution is the isolation effect that NiO (or CoO) is isolated by MgO, which inhibits the metal-metal bond formation during the reduction. (C) 2009 Elsevier B.V. All rights reserved.