Abstract: At low temperature,the LNG engineering materials should have the characteristics as being hard to have embrittlement,high toughness/strength,and excellent workability and weldability,etc.From the crystal structure of view,the mechanism of high toughness/strength of the austenitic stainless steel pipe under ultra-low temperature is analyzed.And the performances of the LNG engineering-purpose stainless steel tubular material and other metal materials for the same service (9%Ni,invar alloy,aluminum alloy and copper alloy) are compared.Accordingly the welding consumable for the LNG engineering-purpose pipe is selected.