Abstract: The welding ability of Alloy X and Q235B steel was researched,and the main problem is that the heat affected zone（ HAZ） in the side of Q235B steel has a low impact value,which results in that the impact toughness of welded joint can’t meet the quality requirements.The method of surfacing welding was taken to optimize fusion ratio and to adjust the weld craft parameter by controlling welding heat input and inter-pass temperature. Furthermore,it can effectively improve the impact toughness of HAZ and the mechanical properties of the welded joints meet the design requirements completely.