In this study, crystal structural changes and dielectric properties of $(1-x)Pb(Yb_{1/2}Nb_{1/2})O_3-xPbTiO_3$ ((1-x)PYN-xPT) solid solutions were measured and analyzed with respect to the $PbTiO_3$ (PT) contents ($0.40{leq}x{leq}0.60$). From X-ray diffraction (XRD) measurements, (1-x)PYN-xPT solid solutions showed changes of the crystal structure from pseudocubic ($0.40{leq}x{leq}0.44$) to tetragonal ($0.52{leq}x{leq}0.60$) on increasing PT contents and exhibited the coexistence of pseudocubic and tetragonal phase near the morphotropic phase boundary (MPB) composition ($0.46{leq}x{leq}0.50$). The dielectric constant showed a maximum value at x = 0.46 and the maximum values in (1-x)PYN-xPT decreased with higher PT contents. The phase transition temperatures of (1-x)PYN-xPT solid solutions increased over the whole composition ranges tested ($0.40{leq}x{leq}0.60$).