According to inverse magnetostrictive effect, the dynamic magnetic field of giant magnetostrictive material (GMM) under magnetoelastic force in magnetization process was derived based on the minimal value principle of energy combining with magnetic theory. Then the frequency characteristics of eddy current loss, hysteresis loss and complex permeability were studied. The simulative and experimental results were used to analyze the influence of magnetic loss on the temperature rise characteristic of giant magnetostrictive actuator (GMA). These results indicate that the calculational result of the eddy current loss is in a good agreement with that of the simulation, so the calculation method can be used to study the loss of GMM under low-middle frequency, and the change of complex permeability under high frequency increases hysteresis nonlinearity of magnetic field. Also it indicates that the axial temperature distribution of GMM in actuator varies with the frequency. The experimental result confirms the validity of calculation and simulation. Finally the effect of forced water cooling in GMA is discussed, and the above studies have a significant guidance for the analysis, design and application of GMA.