The invention relates to a new energy power station AVC system and a reactive real-time regulating quantity calculation method thereof. The method comprises the steps that by means of a series of characteristic values, a model which generates variation for parameters such as high voltage side bus voltage, middle voltage side bus voltage, low voltage side bus voltage and power station output reactive power after an electric generator increases or reduces reactive output, a middle voltage side bus or a high voltage side bus compensates reactive power, or the two-stage transformer tapping switchposition is raised or lowered is built. When the power station AVC system runs on the spot, the model can serve as an internal algorithm to be introduced into the AVC system, the AVC system is assisted to make a reactive compensation switching strategy rapidly and accurately, and a new power station AVC system is generated. The new AVC system can meet the rapid adjustment response time requirements of voltage and reactive power, the voltage and reactive power of the power station are maintained to be within the given target value range at any time, and the electric energy quality output by thepower station is improved.