Abstract: Oil-impregnated paper capacitive bushing, as one of the core current-carrying components of a transformer, has functions of support, current diversion and insulation. The insulation performance is crucial to the stability and safety of transformer operation. In order to reduce insulation faults caused by oil-paper partial discharge during the operation of oil-immersed paper bushings, this paper adopts nano-modulation technology to improve the dielectric and electrical properties of oil-immersed insulating paper for the main insulation of bushings. Taking 20 kV oil-paper capacitor bushing as the research object, a combination of simulation and experiment is used to investigate the effect of nanoparticles on the electric field distribution and partial discharge initial voltage of the main insulation of the casing core. The experimental results show that the nano-TiO₂ particles can improve the surface microstructure of insulating paper, reduce the relative dielectric constant and the peak electric field intensity in the casing core, and increase the partial discharge initial voltage of the casing core. This provides a reference for improving the insulation performance of oil-paper capacitive bushings.