The　effect　of　different　molar　ratios　of　Y2O3　and　Y(NO3)(3)　on　the　microstructure　and　electrical　response　of　ZnO-Bi2O3-based　varistor　ceramics　sintered　at　1　000　A　degrees　C　was　investigated,　and　the　mechanism　by　which　this　doping　improves　the　electrical　characteristics　of　ZnO-Bi2O3-based　varistor　ceramics　was　discussed.　With　increasing　amounts　of　Y(NO3)(3)　or　Y2O3　in　the　starting　composition,　Y2O3,　Sb2O4　and　Y-containing　Bi-rich　phase　form,　and　the　average　grain　size　significantly　decreases.　The　average　grain　size　significantly　decreases　as　the　contents　of　rare　earth　compounds　of　Y(NO3)(3)　or　Y2O3　increase.　The　maximum　value　of　the　nonlinear　coefficient　is　found　at　0.16%　Y(NO3)(3)　or　0.02%　Y2O3　(molar　fraction)　doped　varistor　ceramics,　and　there　is　an　increase　of　122%　or　35%　compared　with　the　varistor　ceramics　without　Y(NO3)(3)　or　Y2O3.　The　threshold　voltage　V　(T)　of　Y(NO3)(3)　and　Y2O3　reaches　at　1　460　V/mm　and　1　035　V/mm,　respectively.　The　results　also　show　that　varistor　sample　doped　with　Y(NO3)(3)　has　a　remarkably　more　homogeneous　and　denser　microstructure　in　comparison　to　the　sample　doped　with　Y2O3.