Abstract: In order to meet the requirement of welding of X80 pipeline steel, a low alkali slag system of Mn-Ni-Mo-Ti-B alloy self-shielded flux cored wire based on BaF₂ was developed and the microstructure and mechanical properties of joint welded by the welding wire were analyzed. The results show that the microstructure of weld included acicular ferrite, granular bainite and a small amount of M-A island and the microstructure of heat affected zone mainly included granular bainite and bainite ferrite. The tensile strength of the welded joint was 711 MPa and yield strength was 565.7 MPa. The impact energy was 155 J at room temperature and 144.7 J at -20℃. The properties of the weld joint could fully meet the standard requirement of oil pipeline construction project.