Abstract: Trans-varestraint test was used to investigate the solidification cracking mechanism of 690 nickel-based alloy surfacing metal.Results show that, the solidification cracking susceptibility of 690 nickel-based alloy surfacing metal is closely correlated with the segregation process during welding, which is greatly influenced by Nb.The solidification temperature of 690 nickel-based alloy surfacing metal falls when the Ni, Nb-rich phases segregate on the grain boundary or subgrain boundary, which induces that the ductility decreases and the appearance is fined.Then, cracking initiates and expands along the finer grain boundary or subgrain boundary during the solidification process.Furthermore, in 690 nickel-based alloy surfacing metal, Mn weakens the negative influence of Nb on solidification cracking resistance to some extent by restraining the segregation effect of Nb, and then the cracking resistance is improved.