Abstract: As an execution organ,the composite switch always plays an important role in the reactive power compensation system,which is suitable for the on-off control of the reactive power compensation capacitor of the 660 V mine electrified wire fence.This paper described the working principle and the connecting ways of the main circuit and elaborated the switching capacitor entire work process of composite switching in detail.Finally,the simulation model of the whole system is set up by comparing different switching modes and times based on the simulation of MATLAB,achieving a dynamic simulation of reactive power compensation.