A high speed position servo system is important for performance improvement of motion control in several industry applications. It often has the desired position reference. An industrial servo system has the limitation values based on each output of actuator and power amplifier. Hence, a high speed position servo system should keep the tracking control for the desired position reference within the limitation values. Moreover, an industrial servo system must realize the robust control against load torque and load inertia variation. An ordinary position servo system has the complicated control structure caused by the triple minor control loops. On condition of both load inertia variation and the saturation caused by current & voltage limitation, an industrial servo system sometimes has a large overshoot and an oscillated response. Therefore, for the desired quick position reference, it is difficult for a high speed position servo system to keep the robust tracking control against load inertia variation within each limitation of motor current and motor voltage. In order to overcome this problem, this paper proposes a new robust high speed position servo system considering current & voltage limitation and load inertia variation, which is based on disturbance observer. The experimental results confirm that the proposed system realizes the desired & quick & robust response keeping each limitation of speed, current and voltage on condition of both full load torque and three times load inertia variation.