Abstract: To address the issues of poor performance in additively manufactured magnesium-lithium alloy components and the lack of mature commercial wire materials, this paper proposes a bypass gas-shielded metal arc directional energy deposition (Bypass-GMA DED) technique. This method uses AZ31B wire as the main feedstock and introduces strip-shaped LA141 master alloy via a bypass feed to produce magnesium-lithium alloys with both high strength and ductility in situ. The forming process parameters for this alloy are a welding current of 110 A, a wire feed rate of 7.5 m/min, and a strip feed rate of 1 m/min. Under these parameters, the deposited components exhibit good formability and few pores. The microstructure and mechanical properties of the components were analyzed. The results indicate that, compared to the AZ31B magnesium alloy, the average grain size of the as-deposited magnesium-lithium alloy is reduced. Due to the accumulation of heat input, the grain size gradually increases from the bottom to the top, consisting primarily of equiaxed grains; The average ultimate tensile strengths in the transverse and longitudinal directions were 318.0 MPa and 305.7 MPa, respectively, with elongations of 20.2% and 17.4%, respectively, achieving a favorable strength-to-ductility ratio and providing a new approach for the additive manufacturing of magnesium-lithium alloys.