Abstract: The excitation controller is applied to control the excitation current of the generator, which is the kernel part of the generation system. The excitation controller with wide bandgap power devices (such as SiC or GaN) has the advantages of low loss and high switching frequency. However, the switching performance of power devices will be affected by parasitic capacitance in the circuit. The switching loss increases. The oscillation and electromagnetic interference problems occur. The parasitic capacitance of excitation winding is an important part of the excitation control circuit. The reduction of the parasitic capacitance can improve the operating characteristics of the excitation controller. In order to explore effective methods to reduce the parasitic capacitance, an accurate analytical model of parasitic capacitance of multi-layer windings is proposed in this paper. The turn-to-turn distance, turn-to-core distance and layer-to-layer distance are taken into consideration. The key factors affecting parasitic capacitance is obtained by calculating the sensitivity of parameters by Taguchi method. The variation law of parasitic capacitance is studied. An effective method is obtained to reduce the parasitic capacitance of multi-layer stator circular windings when the slot space of excitation winding is limited. The accuracy of the mathematical model and the effectiveness of the parasitic capacitance reduction method are verified by experiments.