The invention provides a method for setting up a reactive power compensation device model based on a controlled alternating current source. The method includes the following steps of measuring the voltage of an installation point of a reactive power compensation device and the voltage of a control point of the reactive power compensation device, calculating control voltage deviation, setting up the reactive power compensation device model, and conducting calculating to obtain an amplitude signal, a frequency signal and a phase angle signal of the controlled alternating current source. According to the method, by using the controlled alternating current source and a grid interface, by controlling the amplitude, the phase angle and the frequency of the current of the controlled alternating current source and particularly by keeping the phase angle of the current of the installation point 90 electrical degrees greater than the phase angle of the alternating current source, the ideal control of the output power of the reactive power compensation device is achieved. The method can be easily and extensively applied to various power generation systems which include wind turbine generators, photovoltaic power generating systems, battery energy storage systems, ocean power generating systems, micro gas turbines and the like and are connected with a power grid through power electronic equipment interfaces, and can be easily and extensively applied to novel power electronic interface new energy power generating systems which are rapidly developing and constantly emerging.