Computer modeling and simulation for the Pb(Zr1-xTix)O3 (PZT) system reveal the role of polar anisotropy on the giant anhysteretic response and structural properties of morphotropic phase boundary (MPB) ferroelectrics.It is shown that a drastic reduction of the compositiondependent polar anisotropy near the MPB flattens energy surfaces and thus facilitates reversible polarization rotation.It is further shown that the polar anisotropy favors formation of polar domains,promotes phase decomposition and results in a two-phase multidomain state,which response to applied electric field is anhysteretic when the polar domain reorientation is only caused by polarization rotation other than polar domain wall movement.This is the case for the decomposing ferroelectrics under a poling electric field with the formation of a two-phase multidomain microstructure,wherein most domain walls are pinned at the two-phase boundaries.Indication of the microstructure dependence of the anhysteretic strain response opens new avenues to improve the piezoelectric properties of these materials through the microstructure engineering.