To study the impact of mechanical structure on the torque loading performance of a friction based electro-hydraulic load simulator, the loading principle of the proposed load simulator is described, and a prototype of one-way load simulator is built. The linear mathematical model of the proposed load simulator is established, and a PID plus feed-forward controller is designed to improve precision of the torque tracking control without any extra torque compensation. The impacts of the spring stiffness, the frictional performance of the friction discs, etc on the torque loading performance are studied experimentally. Then, the experimental studies are focused on the small amplitude torque loading performance of the proposed load simulator with severe disturbance of the steering engine. The experimental results show that the friction based torque loading method has no structural extra torque, and can achieve high torque loading performance. Besides, to further improve the torque loading performance, the stiffness of the spring should be optimized, the friction disc material with excellent friction properties is needed and the high performance controller should be designed.