The MSMA is a new type of functional materials, which has biggish driving force and controllable displacement. The new type of linear servo actuator was designed based on characteristics of magnetic control and mechanism of shape changing of Magnetic-control Shape Memory Alloy (MSMA). Spring was used by the actuator to recover the deformation, DC coils was employed to generate biasing magnetic field and AC coils were applied to provide magnetic field which was controllable. The pilot servo valve was simplified and molded without considering the effects of magnetic sluggish, and was numerically simulated by using MATLAB/SIMULINK software. Moreover through rational parametric design, the drawing of displacement curve of system output and drawing of bode of system were gotten. The rationality of structural design of the new type of actuator is validated.