The invention discloses an automatic reactive compensation controller, which comprises a DSP processor, a voltage sampling circuit, a current sampling circuit and a memory, wherein the DSP processor is provided with a threshold presetting module and a data processing module; a delay threshold and a voltage switching threshold are preset through the threshold presetting module and are stored into the memory; the voltage sampling circuit carries out voltage data collection according to the preset delay threshold; and the data processing module compares the collected voltage data with the preset voltage switching threshold and controls intelligent capacitors to act according to the comparison result. The preset delay threshold on the DSP processor can be freely set according to the characteristics of actual rural public variable load and seasonal changes, so that the mean value calculated by five-times voltage or current data collection of each fluctuation is relatively accurate; and the problem that the automatic reactive compensation controller frequently transmits intelligent capacitor switching instructions due to volatile value data fluctuation is solved.