Abstract: Addressing the manufacturing process and equipment structural characteristics of the Φ460 mm Assel mill,the automatic on-line cold-centering machine for the round billet is developed.Described here are the mechanical system and the control system of the centering machine.The functions of the centering machine include acquiring the position data of the round billet surface via the laser displacement sensor,and the center of the billet with the least squares method,and then sending instructions to the power device via the computer to get the drill carbon rod moving to the billet center position to start electric spark drilling.The machine is capable of making satisfactory holes,and features good production consistency,reasonable cost,and stability and liability.