Abstract: The low temperature toughness test,microstructure analysis,TEM analysis were conducted in high strength steel SAW deposited metals with different Mn/Si.The relations between microstructure,form of inclusion and low temperature toughness were investigated.The result indicates that with the change of Mn/Si in high strength steel SAW deposited metals,the low temperature toughness changes.When Mn/Si=4~8,the deposited metals toughness attained 100 J at-50℃ and when Mn/Si<4 or >8,the toughness declined.