Sensitivity of Nb to high-temperature ductility dip crack(HTDDC)of deposited metal of Inconel 690 welding wire was studied in detail.Strain to fracture test and high-temperature tensile test were selected as the test methods to study the sensitivity of HTDDC.The de-posited metals of four kinds of welding wire were observed and analyzed by OM and SEM.Experiment results show that Nb can effectively improve the ability of Inconel 690 to resist HTDDC and reduce the crack sensitivity of deposited metal.The mechanism of HTDDC is the grain boundary strength of deposited metal is lower than the intragranular strength.The(Nb,Ti)C can effectively block the grain boundary sliding and improve the resistance to deformation of the grain boundary.