High-thermal-conductivity silicon nitride ceramic substrates are indispensable components for nextgeneration high-power electronic devices because of their excellent mechanical properties and high thermal conductivities,which make them suitable for applications in complex and extreme environments.Here,we present an overview of the recent developments in the preparation of high-thermal-conductivity silicon nitride ceramics.First,the factors affecting the thermal conductivity of silicon nitride ceramics are described.These include lattice oxygen and grain boundary phases,as well the oxygen content of the crystal lattice,which is the main influencing factor.Then,the methods to prepare high-thermal-conductivity silicon nitride ceramics are presented.Recent work on the preparation of high-thermal-conductivity silicon nitride is described in detail,including the raw materials used and the forming and sintering processes.Although great progress has been made,the development of a high-quality,low-cost fabrication process remains a challenge.Nevertheless,we believe that high-thermal-conductivity silicon nitride substrates are promising for massive practical applications in the next generation of high-power electronic devices.