Electrocaloric　cooling　based　on　ferroelectrics　is　an　eco-friendly　technology.　BaTiO3　(BT)-based　ferroelectric　ceramics　possess　a　high　electrocaloric　effect,　which　is　significantly　affected　by　grain　size.　Herein,　fine　and　large　grains＇　contributions　to　electrocaloric　and　related　properties　in　BT-based　ceramics　are　revealed　via　tuning　sintered　dwelling　time　(t(s))　in　discontinuous　grain　growth　(DGG)　process　with　fine　and　large　grains　coexistence.　With　increasing　t(s),　grain　size　change　can　be　divided　into　two　stages.　The　main　change　is　the　large-grain　size　(＞100-200　mu　m)　and　number　in　the　beginning　DGG　stage,　and　the　properties＇　evolutions　are　mainly　contributed　by　large　grain　change.　The　bigger　grain　size　of　large　and　fine　grains　contributes　to　the　higher　electrocaloric　property,　sharper　phase　transition,　ferroelectric　polarization　(change　rate),　and　coercive　field.　In　the　subsequent　stage,　fine　grains　gradually　grow　up　(similar　to　4.0-5.0　mu　m)　while　large-grain　size　decreases　slightly.　Here　the　properties＇　evolutions　are　influenced　by　the　competitive　contributions　between　fine　and　large　grains.　Large　grain　contribution　is　mainly　attributed　to　the　domain　size　effect,　and　fine　grain　contribution　should　embrace　the　domain　size　effect　and　grain-boundary　pinning　effect.　This　work　contributes　to　a　broad　understanding　of　fine/large　grain　contributions　in　the　promising　BT-based　electrocaloric　ceramics.