Based on the working principle of giant magnetostrictive actuator (GMA), a mechanical structure with segmented bias magnetic field and oil cooling system is designed. The 3D model of the GMA is established and its magnetic field and temperature field are simulated with finite element analysis software. The simulation results show that the segmented bias magnetic field method can obtain better bias performance, the oil cooling system can greatly lower the GMA’s temperature. A force test platform is set up, then the static and dynamic output force characteristics of the GMA are studied, respectively. The experimental results indicate that the output force has positive correlation with the driving current. Excited by DC, the output force of the GMA has hysteresis nonlinearity and is greatly influenced by the GMA’s temperature but slightly influenced by the external mechanical constraint force. Meanwhile, the GMA can accurately track the signals without doublefrequency effect when driven by AC. This represents that segmented bias magnetic field has excellent bias effect, high precision and fast dynamic response speed.