Dielectric properties of the Pb(Sc1/2Nb1/2)O3-PbTiO3(PSN-PT (1-x)/x) solid solutions were measured. Phase transition between relaxor and normal ferroelectric states was confirmed for 0.40<x<0.50. The Curie temperature was linearly increased with increasing PbTiO3 contents and the normal ferroelectric properties were strengthened with the increase of PbTiO3 contents. Lanthanum was doped for the MPB composition of PSN-PT(57.5/42.5) and the dielectric properties were measured. The maximum dielectric constant was greatly increased with increasing La contents below 7 wt% and Curite temperature was increased with increasing La contents. The La-PSN-PT (5/57.5/42.5) composition showed 48,000 of the maximum dielectric constant. The introduction of La into PSN-PT(57.5/42.5) composition contributed to the for-mation of the normal ferroelectrics