Silicon nitride ceramics not only have high mechanical properties, but also have strong wave-transmitting properties, high thermal conductivity and biocompatibility, which are regarded as the most excellent ceramic materials. Dense silicon nitride ceramics as bearing balls are widely used in the fields of the engineering industry; porous silicon nitride ceramics as wave-transmitting materials are extensively applied in the fields of the aerospace industry. With the continuous in-depth research on silicon nitride ceramic materials, their excellent properties of high thermal conductivity and biocompatibility have been gradually developed by researchers and their application fields are broadened. This article describes in detail the preparation methods of silicon nitride powder, and reviews the research progress of silicon nitride ceramics as structural ceramics in the areas of machinery, military, and aerospace industries. In addition, it also introduces the application of silicon nitride ceramics as functional ceramics in the fields of semiconductors and biopharmaceuticals. Finally, the future development of silicon nitride ceramics has prospected.