Chemical　doping　is　favored　by　academia　as　well　as　industry　because　of　its　effectiveness　in　attuning　to　the　properties　of　piezoceramics.　Although　significant　progress　has　been　made,　few　reports　have　focused　on　the　role　and　overall　effect　of　substituted　ions.　Based　on　the　tendency　of　special　crystals　such　as　ZnO　toward　spontaneous　growth,　this　study　applies　the　concept　of　composite　modulation　to　conventional　doping;　the　CuO-modified　0.2Pb(Zn1/3Nb2/3)O-3-0.8Pb(Zr1/2Ti1/2)O-3(PZN-PZT)　system　has　been　used　for　verification　of　the　proposed　method.　The　results　show　that　copper　ions　enter　the　perovskite　matrix　to　specifically　replace　the　zinc　ions　causing　lattice　distortion　and　increasing　the　rhombohedral　phase　(RP)　content.　Furthermore,　the　substituted　zinc　ions　enter　the　grain　boundaries　and　grow　into　a　secondary　phase　ZnO,　based　on　their　spontaneous-growth　tendency;　the　induced　heterogeneous　interfacial　effects　lead　to　refinement　of　the　domain　size　and　enhancement　of　the　interface　polarization.　The　combined　effects　of　the　lattice　substitution　and　composite　modulation　promote　a　significant　improvement　in　the　piezoelectric　coefficient　of　the　CuO-modified　PZN-PZT　system　compared　with　its　pure　counterpart.　The　dual　function　of　doping　demonstrated　in　this　study　is　expected　to　further　contribute　to　the　preparation　and　performance　improvement　of　the　other　piezoelectric　composites.