Abstract: The microstructure of the weld metal with different Ni contents was characterized and analyzed by using OM, FEGSEM equipped with EDX and TEM. The solidification mode was also discussed by Thermol-Calc software. The results show that with the increase of the Ni content, the microstructure mainly composed of lath bainite and lath martensite became the mixture of martensite and coalesced bainite. With the increase of the Ni content, the strength of weld metal increased and the low temperature toughness of weld metal was good. The weld metal with higher Ni content solidified completely as austenite, causing dendritic segregation of Mn and Ni.