Dielectric　responses　of　multiscale　defects,　including　electron　trapping　behaviours　of　intrinsic　point　defects　in　grains,　heterogeneous　interface　of　depletion/intergranular　layers,　and　dynamic　responses　of　interface　states　at　grain　boundaries,　were　investigated　in　ZnO　varistor　ceramics　via　the　DC　ageing　process.　The　dielectric　relaxation　peaks　corresponding　to　zinc　interstitials　and　oxygen　vacancies　increased,　revealing　that　the　donor　densities　gradually　increase　with　ageing　time.　Dynamic　response　of　the　interface　states,　which　were　observed　to　undergo　significant　dc　conductance,　using　traditional　dielectric　spectroscopy,　is　unveiled　based　on　an　optimised　(∂Ε＇/∂lnω)/Ε′　spectroscopy.　The　energy　level　of　interface　states　monotonously　decreased　while　the　relaxation　peak　value　increased,　corresponding　to　decreased　interface　states　with　degradation　time.　Collectively,　the　degradation　of　Schottky　barrier　during　DC　ageing　process　is　discussed　based　on　multiscale　defect　responses　with　the　help　of　the　(∂Ε＇/∂lnω)/Ε′　spectroscopy.　©　2020　Elsevier　Ltd　and　Techna　Group　S.r.l.