The effects of compressive stress parallel and perpendicular to the polar axis of PZT ceramics on the nonlinear electromechanical behavior of the materials has been experimentally studied. A domain-switching model that divides each 180° switching to two successive 90° switching is proposed to explain these effects. In the case of stress parallel to the polar axis, domain switching in the ceramics is approximately axisymmetric and can be simulated by an analytical model. While in the case of stress perpendicular to the polar axis, domain switching is three-dimensional and cannot be simplified. The simulated results that match the experiments well show the validity of the proposed domain-switching model.