Abstract: Detailed in the paper are the microstructure of the X8 0M steel plate for SNG-linepipe-making and changes of its properties shown before and after pipe-making process.Based on the available data and engineering parameters the service conditions of the steel pipe are analyzed with the calculation formula of fracture toughness.The result reveals the following facts.The X80M steel plate is of the microstructure formed mainly of acicular ferrite, and has excellent low-temperature toughness.After pipe-making process, the material's mechanical properties like yield strength, tensile strength, yield ratio and hardness are more or less enhanced, while its low-temperature toughness is reduced.Moreover the X80M linepipe also has excellent safety performance.Even in case of the effect by hydrogen, the X80M linepipe can still assure of safe operation provided the transmission pressure is consisten enough.