Abstract: In order to optimize the welding parameters of X80M pipeline steel under the deep penetration tungsten inert gas welding（DP-TIG） process, an orthogonal experiment was conducted on the welding current and welding speed parameters during the DP-TIG welding process using flat plate butt welding（base metal self melting）. The influence of DP-TIG welding process on the forming effect, microstructure and mechanical properties of pipeline steel joints on both sides was analyzed,and the optimal welding process parameters were obtained. The results show that under the DP-TIG welding process, defect free and well formed welding joints are obtained. Due to the high heat input and large cooling gradient, the fusion line of the weld is clearly visible, and the joint structure is mainly composed of ferrite and bainite. The average grain size of the weld zone, coarse grain zone and fine grain zone is 7.6 μm, 13.6 μm and 8.1 μm. The tensile strength and yield strength are 697 MPa and 627 MPa, respectively, and the fracture surface of the tensile specimen is located at the position of the base metal.The impact absorbed energy of the weld seam and heat affected zone is 184 J and 203 J, respectively.