The invention relates to a feedthrough line for oxide gradient multiphase ceramic nuclear power, and preparation and application thereof. The feedthrough line comprises a multiphase ceramic inner core, a transition layer is arranged on the outer layer of the multiphase ceramic inner core, and an insulating ceramic layer is arranged on the outer layer of the transition layer. Accordingly, a singlesintering forming process is innovatively adopted, and the prepared electric feedthrough line has the advantages of being high in air tightness, resistant to high temperature, high pressure, corrosion, radiation and overload and the like, and the stringent requirements of a new generation nuclear power plant such as a high temperature gas cooled reactor for the electric feedthrough line can be met.