High temperature H2O/CO2 co-electrolysis using solid oxide electrolysis cells is a promising method to produce syngas (a mixture of H-2 and CO), which can be used as feedstock of the Fischer-Tropsch reaction to synthesize value added liquid fuels. However, the overall solid oxide co-electrolysis process is complicated, involving both electrochemical reaction and reverse water gas shift reaction. The present paper offers a brief overview of the fundamental knowledge related to solid oxide co-electrolysis cells, such as working principle, thermodynamics and Nernst potentials. In addition, chemical equilibrium co-electrolysis models are reviewed, which have been developed to reveal the systematic relationship between the operating conditions and the Nernst potential as well as the gas composition evolution. Finally, the electrochemical performances recently reported on a number of solid oxide co-electrolysis cells are summarized, and cell degradation mechanisms occurred on solid oxide cells using Ni-based cermets cathode are also reviewed. (C) 2016 Elsevier B.V. All rights reserved.