In　the　present　work,　the　phase　transitions　and　relaxor　behavior　of　(1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3)　(PMN-PT,　x　=　0.2-0.4)　ferroelectric　ceramics　have　been　investigated　by　means　of　X-ray　diffraction,　dielectric　spectroscopy,　the　P-E　hysteresis　loop　measurements　and　Raman　scattering　techniques.　Structural　analysis　revealed　that　with　the　increase　of　PbTiO3　content,　PMN-PT　ceramics　experienced　a　gradual　phase　transition　process　from　rhombohedral　to　tetragonal.　It　is　usually　believed　that　such　kinds　of　phase　transitions　resulted　in　the　linear　decrease　of　relaxation　degree.　Surprisingly,　our　analysis　of　the　dielectric　spectra　revealed　that　the　indicator　of　the　degree　of　diffuseness　y　reached　the　maximum　value　near　morphotropic　phase　boundary　(MPB)　(x　=　0.32),　then　decreased　with　the　further　increase　of　PbTiO3　content.　The　large　dielectric　relaxor　feature　near　MPB　may　be　attributed　to　the　formation　of　ordered　nanodomains,　resulting　from　complex　coexisting　nanostructures.　Further,　the　P-E　hysteresis　loop　measurements　and　Raman　analysis　of　the　B-site　cation　order　correlated　well　with　the　dielectric　measurement　results.　It　was　found　that　the　hysteresis　loop　squareness　R　(sq)　received　the　minimum　value　while　the　inverse　of　the　value　of　full　wide　of　half　maximum　(FWHM)　of　A(1g)　mode　reached　the　maximum　value　at　MPB　composition,　which　showed　similar　trends　to　y.