Abstract: The effects of Nb content on microstructure and intergranular corrosion resistance( IGC) of 625 strip surfacing metal were analysed.Resultsshow that the increase of Nb content critically decreases the IGC resistance of alloy. When Nb content is at a low level,the precipitates are mainly Nb C and few Laves phase,so a high corrosion resistance is exhibited. With the increase of Nb content,severe dendritic segregation occurs and segregation and growth of Laves phase enriched with Nb,Mo and Si are promoted. The blocky Laves phase causes Chromium depleted zone and inhomogeneity of chemical composition around interdendritic regions,where is a priority for IGC,thus the corrosion rate is sharply increased.