Abstract: Researched on in the paper are the effects by different heat treatment schemes on the mechanical properties and microstructure of the Gr3 low-temperature seamless steel tube,based on which the best heat treatment process is summarized.It is regarded via the analysis that thanks to the normalization process and the normalization+tempering process,the as-hot-rolled Gr3 low-temperature seamless steel tube has its grain refined,microstructure adjusted,and overall mechanical property improved;and rather desirable low-temperature toughness of the pipe can be obtained,and both the pipe's-100℃longitudinal impact energy and traversal impact energy are higher than 100 J due to the process of normalization at 850℃+tempering at 650℃.