Abstract: Aiming at shortcomings of the traditional reactive power compensation devices,this paper designs the system structure of a new generation of reactive power compensation device STATCOM based on 1 140/660 V power supply systems.The components of system and the methods of software design are introduced in detail.Through the simulation in MATLAB environment,the simulation results show that this device has the merit of fast transient response,high power factor,low harmonic injection and so on.