With increased penetration of power electronics interfaced renewable generation such as photovoltaics and wind turbines, the power gird will face huge challenges. The virtual synchronous generator(VSG) technologies, which learn from the operation of the traditional power system to control the inverter to mimic a synchronous generator, can overcome the shortages of power electronic equipment, such as low inertia and damping. This is of great significance to improve the integration of distributed generation and to build the smart grid. This paper presents the principles and basic characteristics of virutal synchronous generator. The current research results are reviewed from the aspects of methematical model, control strategies and stability analysis. The inertia, frequency and voltage regulation functions of VSG have been realized, and the operation and stability characteristics of sigle-machine system has been widely discussed. However, the high-frequeny characteristics, storage systems, transient characteristics and interaction mechanism of massive VSG still need to be researched. Finally, the application senarios in power system and practical engineering applications of virtual synchronous generator are introduced from the aspects of connection of renewable energy, microgird and VSC-HVDC.