Abstract: The weldability of Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd alloy was investigated.The test results showed that the heat affected zone (HAZ) of Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd alloy weldment exhibit obvious ductility decrease and the 150℃ preheat can improve the HAZ ductility to a certain extent.Combined with alloy system adjustment and appropriate postweld heat treatment,the weldment comprehensive properties were controlled to meet the specifications.Nd-rich particle clusters along the grain boundaries and the inner grain martensite structure were considered to be two essential factors embrittling the Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd alloy weldments.