Abstract: A method and an apparatus for calibrating a tool in a flange coordinate system of a robot are disclosed. The method includes: acquiring a rotation angle of each joint of a robot when a to-be-calibrated tool fasted on an end joint mounting portion of the robot moves to a central point of the to-be-calibrated tool and overlaps with a calibration reference point; acquiring calibration information of a central point of a calibrated tool in a flange coordinate system of the robot; and completing calibration of the central point of the to-be-calibrated tool in the flange coordinate system of the robot according to the calibration information of the central point of the calibrated tool and a rotation angle of the to-be calibrated tool.