Abstract: Successfully developed is theΦ1 219 mm×26.4 mm X80 high-deformation LSAW tube with the proportionally proper ferrite+bainite double phase, high-deformation steel plate as the raw material, and by means of the small JCO forming control and the optimized design of the steel tube welding parameters, and determination of the pipe expansion parameters via the regression analysis.Related test results show that all the mechanical properties of the welded joint of the tube are in conformity to applicable technical requirements, including tensile property, bending property, low-temperature impact property and hardness;mean value of the -10℃ Charpy impact toughness is higher than 200 J, which means a high margin;the Charpy impact toughness of the pipe body, weld seam and the HAZ is good under the serial temperatures as 20, 0, -10, -20, -40, -60℃;the transversal shearing area percentage of the pipe body is being reduced along with falling of the temperature;FATT85% is less than 10%;and no leakage is found during the pressure-boosting process of the hydrostatic burst test.