Abstract: Syngas is an important industrial raw material, and traditional syngas preparation methods mainly include natural gas reforming, coal gasification, etc. However, these methods often come with problems such as high energy consumption and high carbon emissions. The co-electrolysis using Solid Oxide Electrolysis Cell （SOEC） has received widespread attention in recent years due to its advantages of high efficiency, flexibility, and low carbon emissions. The performance degradation of SOEC is an important issue in the co-electrolysis process, mainly due to factors such as sintering of electrode materials, structural degradation of electrolyte, and impurity contamination.These degradation mechanisms can lead to an increase in internal resistance and a decrease in catalytic activity of the electrolysis cell, thereby reducing the yield, energy efficiency, and service life of syngas. The high-temperature operating conditions of SOEC place extremely high demands on the stability and durability of materials, and the development of new materials that are resistant to high temperatures and degradation is currently one of the research priorities.This article describes the basic principles, thermodynamics, kinetics, reaction pathways, and operating conditions of SOEC co-electrolysis for the preparation of syngas. It focuses on the three typical structural structures of SOEC and the performance and degradation mechanism of co-electrolysis. It discusses the nickel migration, nickel aggregation, nickel oxidation of the fuel electrode, Sr segregation of the air electrode and interface stratification of the air electrode/electrolyte, as well as the poisoning of the air electrode by the metal in interconnect. It also points out the challenges faced by CO₂/H₂O co-electrolysis for the preparation of syngas based on SOEC. In summary, the preparation of syngas by SOEC co-electrolysis is a promising technology with significant application potential in low-carbon chemical and energy transformation. Through in-depth research on the reaction mechanism and degradation process of SOEC, it is expected to promote further development and application of this technology.