Provided is an STATCOM control system and method based on improved instantaneous reactive power. The system is characterized by comprising an acquisition circuit, a control circuit, a drive circuit, a main circuit and a protective circuit. The method includes the steps of data collecting, processing, controlling and driving. The system and method have the advantages of being simple in design, low in cost, high in operation speed, capable of increasing real-time response speed of an STATCOM and improving stability of a power system, simple and understandable in detection method, easy to program and beneficial for being widely popularized.