A giant magnetostrictive actuator is designed with strong bias magnetic field. The influence of the strong bias field is introduced, and the corresponding exciting input signal is selected. Magnetic reluctance estimation, approximate linearity between the strain and magnetic field, and a mass–spring–damper system assumption are employed to analyze the actuator’s displacement with low-frequency signal input. An experimental system is designed, and properties of the proposed actuator are tested. With the help of square wave test, appropriate direction of exciting signal for the magnetostrictive actuator is determined. With the help of sinusoidal wave test, the established model is validated and the relationship between the maximum value of the displacement and of the current is analyzed. With exciting frequency lower than 200 Hz, the errors between the calculating and testing results are within 1.0 m, which validates the model.