Abstract: The single-power double-electrode bypass coupled arc welding process was studied. The main electrode is tungsten and the bypass electrode is wire. Firstly, the generation and shunt mechanism of bypass arc was analyzed, and the geometric parameters of double electrode combination were studied by using the built welding test device. Then, H08Mn2Si welding wire was used to conduct surfacing test on the surface of Q235 steel plate.The influence relationship between bypass wire feeding speed and bypass current, welding process stability and heat input of base metal was studied, and the bypass wire feeding speed interval was obtained at different total currents. Finally, the macro-morphology and micro-morphology characteristics of the welds were analyzed. The results show that when the total current is constant, as the bypass current increases gradually, the heat input of the base metal decreases gradually, the weld width decreases significantly, the weld height increases, and the width to height ratio of the weld decreases.The increase of the bypass current makes the width of the weld overheat zone, the penetration depth and the grain diameter decrease significantly.