Molten　salt　is　widely　applied　as　long-term　large-scale　thermal　energy　storage　medium.　The　high　voltage　molten　salt　electric　heater　is　urgent　needed,　which　has　significant　low　cost　advantage.　The　dielectric　ability　and　thermal　conductivity　of　the　filling　powder　in　electric　heating　tubes　are　crucial.　In　this　study,　modified　aluminum　nitride　is　used　as　the　filling　powder　for　the　high　voltage　electric　heater.　The　breakdown　voltage,　thermal　conductivity　coefficient,　and　thermal　diffusivity　of　the　electric　heater　are　obtained.　The　results　show　that　the　highest　thermal　diffusivity,　thermal　conductivity　coefficient,　breakdown　voltage　of　AlN　filled　electric　heater　are　4.7975　x　10　-7　m　2　/s,　1.2479　W/(m　&　sdot;k)　and　3.5　kV,　which　are　6.4　times,　1.8　times　and　1.4　times　than　that　of　traditional　electrical　grade　magnesium　oxide　electric　heater,　respectively.　The　150　mu　m　AlN　treated　under　800　degrees　C　is　considered　as　suitable　filling　material　for　high　voltage　molten　salt　electric　heater.