Abstract: A new rotating arc leading tandem twin-wire co-pool welding method was developed in this paper. The developed method has the seam tracking capability of rotating arc weld. The influence of weld parameters such as welding current, arc voltage, two wire distance and arc rotating on welding formation quality were studied. The results show that with the increase of welding current, the deposition rates increases linearly, while the aspect ratio of weld increases firstly and then decreases in the later. With the increase of arc voltage, the aspect ratio of weld decreases slightly. Based on the study of the distance between two wires, it is found that the weld seam quality is better when the distance is 15mm. Compared with the traditional tandem twin-wire welding, in the rotating arc leading tandem twin-wire welding process, the molten pool bottom becomes flat, and the maximum weld depth decreases, but the average weld depth increases, which is helpful for decreasing the stress concentration on the weld seam. Compared with the single wire rotating arc welding, the deposition rate increases apparently, and the welding undercut phenomenon can be avoided during rotating arc leading tandem twin-wire welding process.