We present numerical and experimental results on the nonlinear bending behavior due to domain wall motion in functionally graded piezoelectric actuator under alternating current (ac) electric fields. A nonlinear finite element method is employed to analyze the dynamic response of functionally graded piezoelectric actuator. A phenomenological model of domain wall motion is used in computation, and the effects of ac electric field amplitude and frequency, number of layers, and property gradation on the deflection of the cantilever actuators are examined. Experimental results, which verify the model, are presented using a functionally graded bimorph. The numerical results agree very well with the experimental values.