With the development of 3D printing technology, additive remanufacturing technology has become one of the means of automatic repair for various defects.Artificial surfacing welding is the main method to repair large casting defects, which has the disadvantages of low efficiency, great injury to workers and low repair qualification rate.Therefore, a process method for automatic repair of defects was proposed by using 3D printing and remanufacturing technology. That was, the 3D model of the workpiece was scanned and reconstructed automatically by using the visual system. The type, distribution and scale characteristics of the defects were determined by comparing the model with the standard CAD model, and 3D point cloud data of each damaged part were obtained.The robot program was programmed and generated automatically according to the defect model, and the actuator was driven to complete the automatic welding repair of each defect successively.The experimental results show that the accuracy of the workpiece defect reconstruction model is within ±0.1 mm, the scanning speed is 1 000 mm/min, the workpiece is repaired by automatic welding without welding defects, and each performance index meets the actual application requirements