Abstract: By the performance assessement of line pipes produced during 1950s~1980s, the paper describes the growing process of line pipes fabricated with X52, X65, and X70 steel materials, including the change of steel materials from semi-killed C-Mn to low carbone alloyed steel, and application of control rolling and accelerated cooling. Some tests on elongation and fracture of steel materials have been made, and test results have been given. The test results show that the low carbone alloye steel has higher toughness, the line pipes have obvious anisotropism, the yield strenghth of steel sample will reduce after cooling leveling, and there is a linear relationship between J integral and CVN.