Abstract: A kind of link long journey cover plate centering mechanism was designed to solve the difficulty,which the machine vision are susceptible to cover plate cutting edge,oxide skin and dust in workshop,in existing hydraulic support link robot welding workstation. It is mainly made up of the main body frame,driving mechanism,centering module,supporting module,control system,shield and peripheral accessories.It adopts a special mechanism which can achieve two directions centering by one direction power,with servo control system to achieve precise centering of link cover plate. The actual welding production test shows that the centering accuracy of centering mechanism is no more than 0. 5 mm for link cover plates with different shapes and sizes,and the maximum unilateral clearance of link cover plates after assembly is measured to be 2 mm,meeting the welding requirements. With the increase of the length-width ratio of the cover plate,the rigidity of the cover plate gradually weakens and the phenomenon of vertical bending occurs,which leads to the increase of the maximum gap difference between the two sides of the link cover plate. At the assembly gap of 2 mm,the robot welding process is stable and the cover plate weld seam is good. The link cover plate centering mechanism has high centering accuracy,strong adaptability and high practical value.