Abstract: To improve the stability of welding technology and reduce the post-weld repair due to defects like surface imperfections in key steel structure,a new method by applying auxiliary electric field between the slag and metal during submerged arc welding to guide electric current was developed. The electric signal instrument was used to collect arc voltages for statistics and analysis. The results show that the electric conductivity of molten slag can be improved with tungsten electrode as the cathode,and the electrons are guided into the arc centre to contract the welding arc. Meanwhile,positive and negative ions in the molten slag and weld pool metal migrated to the interface and combined into active oxides with low surface energy. Thus the wetting and spreading performance of molten slag on the surface of weld pool metal are improved. With the beneficial effect brought by the auxiliary electric field,the weld surface is smooth,the appearance of weld and especially the consistency of weld width are improved. Also,the welding process is more stable.