A system for controlling a robot includes a control portion (7) for supplying a control signal to and receiving a control signal from a servo unit (6) for carrying out a signal supply and a signal feedback to an electric motor (5) for driving a shaft executing a Z-axis linear motion, and threshold value supply portion (8) for supplying a threshold value to the control portion. Based on a comparison between a motor torque instruction value and a threshold value supplied from the threshold value supplying portion, an alarm is delivered and the process subsequently proceeds to a step of dealing with an abnormal condition when said motor torque instruction value becomes greater than a predetermined threshold value.