Abstract: Dielectric functionally graded materials (D-FGMs) enable the uniform regulation of electric fields within insulating media and along their surfaces by tailoring dielectric permittivity and electrical conductivity, thereby demonstrating significant potential for high-voltage insulation devices. This review systematically summarizes the gradient configurations of D-FGMs and the advanced fabrication techniques employed for their preparation. Furthermore, recent progress in the application of D-FGMs to high-voltage insulation devices, including high-voltage power module packaging, insulators, and insulating films, is comprehensively reviewed. D-FGMs effectively mitigate local electric field distortion at triple junctions, solid-gas interfaces, and within insulating films, thereby significantly enhancing insulation performance. These materials represent a promising strategy for improving the reliability of high-voltage insulation devices. Finally, future perspectives are discussed regarding precise gradient structure design, intelligent manufacturing, and synergistic regulation under multi-field coupling conditions.