(1-x)Pb(Hf1-yTiy)O3-xPb(Yb0.5Nb0.5)O3 (x=0.10-0.44, y= 0.55-0.80) ceramics were fabricated. The morphotropic phase boundary (MPB) of the ternary system was determined by X-ray powder diffraction. The optimum dielectric and piezoelectric properties were achieved in 0.8Pb(Hf0.4Ti0.6)O3-0.2Pb(Yb0.5Nb0.5)O3 ceramics with MPB composition, where the dielectric permittivity epsilon r, piezoelectric coefficient d33, planar electromechanical coupling kp, and Curie temperature Tc were found to be on the order of 1930,480pC/N, 62%, and 360 degrees C, respectively. The unipolar strain behavior was evaluated as a function of applied electric field up to 50kV/cm to investigate the strain nonlinearity and domain wall motion under large drive field, where the high field piezoelectric d33* was found to be 620pm/V for 0.82Pb(Hf0.4Ti0.6)O3-0.18Pb(Yb0.5Nb0.5)O3. In addition, Rayleigh analysis was carried out to study the extrinsic contribution, where the value was found to be in the range 2%-18%.