We developed a robot-assisted fracture reduction system (FRAC-Robo) to assist anatomical reduction and to maintain reduction during internal fixation while recording the procedure in a log. We conducted two experiments before using FRAC-Robo clinically. In the first experiment using the FRAC-Robo system, we measured the maximum force and torque required to pull and rotate the limbs of healthy conscious volunteers until they felt pain or abnormality. The average maximum traction force applied to the lower limb was 250.7 N, and the average maximum torque was 5.6 Nm in internal rotation and 7.6 Nm in external rotation for 30 degrees of abduction of hip. In the second experiment, we measured the traction force and rotation torque during the reduction of proximal femoral fractures. The average traction force and rotation torque needed for reduction were 215.9 N and 3.2 Nm, respectively. On the basis of these results, we consider that FRAC-Robo can generate sufficient force and torque to reduce femoral fractures safely.