Reactive power compensation for reactive power compensation, it is in electronic power system to increase the power factor of the effect, reduce power transformer and transmission line loss, improve the efficiency of power supply, improve power supply environment. And the power electronic technology is a new application in the power electronics technology, is the use of power electronic devices (for example: GTO, thyristor, IGBT etc) for power conversion and control technology. Therefore, in the automatic control of reactive power compensation technique of power electronics application is a very important technology. The purpose of this paper is to discuss the basic concept of power electronic technology, then discusses the reactive power compensation the principles of automatic control, finally discusses the automatic control of reactive power compensation technique of power electronics application.