In order to achieve a uniform electric field, anti-corona tapes with varying resistance values induced by non-linear resistors were wound on the surface of the main insulation in the slot section of the stator bar. However, the insulating properties of anti-corona materials are influenced by the dispersity and content of conductive fillers. Treatment of the filler changes the dispersion of the packing and the polarization properties of the composite. In this paper, corona-proof composites were prepared by using epoxy resin(EP)as the matrix, graphene oxide (GO) as the filler, and coupling agents KH550, KH560, and KH570 as the grafting materials. The properties about nonlinear conductivity and breakdown characteristics were meticulously tested. The findings revealed that the KH550-GO/EP and KH560-GO/EP composite exhibited notably higher nonlinear coefficients, along with lower dielectric constants and reduced dielectric losses. In contrast, for the same amount of filler doping, the KH570-GO/EP composites demonstrated significantly higher surface resistivity. It is evident that the utilization of various coupling agents for the graft modification of fillers exerts distinct levels of influence on the diverse properties of the matrix resin. Consequently, the elucidation of the mechanisms underlying these different coupling agents presented in this study serves as a valuable reference for future filler modification selections.