hi the present study, the piezoelectricity and polarization of multilayer ceramic actuator, being designed to stack PMN-PZ-PT ceramic layers and Ag-Pd electrode layers alternatively, were investigated under a consideration of geometric factor, the volume ratio of the ceramic to the electrode layers. The actuators were fabricated by tape casting of 0.2Pb(Mg1/3Nb2/3)O-3-0.38PbZrO(3)-0.42PbTiO(3) followed by lamination and burnout & co-firing processes. The actuators of 10 x 10 x 0.6similar to2 mm(3) in size were formed in a way that 60 similar to 200 mum thick ceramics were stacked alternatively with 5 mum thick electrode layer. Increases in polarization and electric field-induced displacement with thickness of the ceramic layer were attributed to change of 90degrees/180degrees domain ratio, which was affected by interlayer internal stress. The piezoelectricity and actuation behaviors were found to depend upon the volume ratio (or thickness ratio) of ceramic to electrode layers. Comparing with the experimental results and simple calculation based on the existence of the internal stress, the relationship between field-induced deformation and the geometry in the actuator was described.