Abstract: ER50-6 carbon steel welding wire was chosen as surfacing welding wire to carry out overhead position MAG surfacing test on Q235B substrate. Effects of three main welding parameters, wire feeding speed, welding speed and wire extension, on weld width and reinforcement of single pass overhead weld was studied by single factor method. Causes of hump defects in welds under different welding parameters were analyzed. Based on this, surfacing strategy for single pass multi-layer overhead position surfacing was proposed, namely reducing heat input, cooling time and disturbance of molten pool. On this basis, 10 layers of single pass multi-layer continuous overhead position surfacing were formed, and tensile test was carried out. The results showed that under welding parameters of wire feeding speed 3.5 m/min, welding speed 0.25 m/min and wire extension 6 mm, forming quality was relatively stable and tensile strength reached 518 MPa, which could meet requirements of some parts with low accuracy requirements. Feasibility of the proposed single pass multi-layer overhead position surfacing strategy was verified, which provided a reference for the selection of welding parameters of overhead position surfacing forming parts.