The giant magnetostrictive material (GMM) is a novel smart material based on magnetostrictive effect, and it is well suited to power ultrasonic transducer. Based on electromagnetic theory and vibration theory, the design and working principle of the magnetostrictive power ultrasonic transducer has been explained. This paper analyzed the dynamic characteristics of giant magnetostrictive materials under the outside magnetic field and deduced the wave equation of Terfenol-D rod, and the steady-state solution to the equation was obtained under given excitation. The speed and acceleration expressions of Terfenol-D were deduced by differentiating with respect to displacement equation. Based on developing mathematical models, computer imitation was made, and the result of modulation was analyzed from external conditions of transducer and inner structure of magnetostrictive material.