In order to meet the requirement of large stroke and high precision displacement, a giant magnetostrictive linear actuator was designed based on the principle of inchworm cumulative displacement. The front clamp mechanism, the back clamp mechanism and the driving mechanism were given a specific time series of excitation signals, and the step-by-step displacement output of the driver was realized by the cooperation of the three. The superimposed flexure hinge was used as the elastic element to improve the force condition of the flexure hinge effectively. The strength check and modal analysis of flexure hinges were carried out by using finite element method. Simplifying flexible hinges into cantilever beams, the equivalent stiffness of superimposed flexure hinges was calculated. The dynamic model of linear actuator was established based on the voltage law, magnetoresistance theory, linear piezomagnetic model and dynamic theory, and the prototype was tested experimentally. The experimental results and simulative results showed that the calculated model was consistent with the experimental results, and the maximum relative error was 1.86%. The stable working voltage range of the giant magnetostrictive actuator was 1~3V, the minimum single-step displacement was 4.55μm, and the maximum single-step displacement was 12.01μm. The maximum frequency was 150Hz, and the maximum speed was 1.34mm/s. The output state of displacement was stable, and the maximum relative error of single step displacement was 2.69%.