Solid solution ceramics of the system xPb(Mg_1/3Ta_2/3)O₃-yPbTiO₃-zPbZrO₃ were prepared by the solid state reaction of powder materials. Ceramic, dielectric, and piezoelectric properties and crystal structures of the system were studied. The system is composed of four crystal phases at room temperature: the cubic, pseudocubic, tetragonal, and rhombohedral. Sintering of the system xPb(Mg_1/3Ta_2/3)O₃-yPbTiO₃-zPbZrO₃ is much easier than that of each end compositions and a well sintered high density ceramics was obtained for the compositions near the morphotropic transformation. Piezoelectric ceramics with high relative dielectric constants and high radial coupling coefficient and low resonant resistance were obtained for the composition near the morphotropic transformation. The composition Pb(Mg_1/3Ta_2i3)_0.125-Ti_0.435Zr_0.44O₃ showed the highest radial coupling coefficient.