Giant magnetostrictive actuator (GMA) is a new type of vibration control driving device. However, due to its complicated internal magnetic circuit, the intensity and uniformity of the magnetic induction in the internal magnetic circuit of GMA will seriously affect the working performance of the actuator. In order to solve the above problems, based on the theory of linear magnetostriction and electromagnetics under static conditions, a finite element model of the GMA was established using the finite element software ANSYS. The impacts of the material parameters of the excitation coil, the magnet and the inner wall of the magnet on the magnetic induction intensity were systematically studied. At the same time, the design principles of reducing the magnetic leakage, increasing the magnetic induction intensity and improving the uniformity of the magnetic induction in the GMM rod were proposed. The intensity and uniformity of the magnetic induction at the axial centerline of the giant magnetostrictive rod were used as the evaluation criteria. Parameters such as the opening and closing magnetic circuit, the axial length of the excitation coil, the magnetic permeability of the material, the air gap, and the radius of the magnetizer were optimized. The results show that when the closed magnetic circuit was adopted, the intensity and uniformity of the magnetic induction were greatly improved. After the optimization of the magnetic circuit, the magnetic induction intensity increased by 0.1 T, and the uniformity increased by 10.27%.