Abstract: In order to decrease the transient over-voltage and surge current caused by the capacitors switching,a new DSP-based synchronous closing device for var compensation is studied in this paper.The capacitor banks are distributed in binary encoding mode and the thresholds of switching capacitors are also optimally allocated.This controller is mainly designed based on DSP2812,and the ATT7022A is used to collect the power gird data.Furthermore,real-time voltage and current zero crossing points of three-phase circuit are obtained,and the permanent magnetic vacuum synchronous circuit breaker ensures the best phase of the capacitor bank switching.This optimal design can greatly enhance the efficiency and accuracy of the device.