In　this　work,　the　effects　of　Sb　doping　on　the　electrical　conductivity　of　fine-grain　0.9(K0.5Na0.5)(Nb1−xSbx)O3-0.1Bi(Ni2/3Nb1/3)O3　(KNNSx-BNN)　ceramics　were　systemically　investigated.　It　was　found　that　the　grain　size　decreases　from　~900　nm　(x　=　0)　to　~340–400　nm　(x　=　0.06–0.08),　and　then　increases　again　to　~700　nm　(x　=　0.10).　This　is　because　the　solubility　limit　of　Sb　doping　is　about　0.08　in　this　ceramic,　and　more　Sb　doping　will　facilitate　the　grain　growth　as　the　sintering　aids.　Impedance　and　conductivity　analyses　reveal　that　the　grain　resistance　and　its　activation　energy　show　a　similar　changing　tendency　with　grain　size,　while　grain　boundary　conductivity　steadily　increases　after　Sb　doping.　In　this　process,　the　grain　contribution　on　ceramic　conductivity　changes　with　grain　size　variation,　and　grain　boundary　contribution　becomes　more　obvious　with　increasing　doping　content.　The　reduction　in　grain　size,　improvement　in　grain　boundary　density　and　doping　ions　entering　into　the　grain　boundary　should　contribute　to　the　evolution　of　electrical　conductivity　properties　after　Sb　doping　in　KNN-based　ferroelectric　ceramics.　©　2022　by　the　authors.