Abstract: To achieve lightweight rocket tanks, replacing conventional aluminum alloys with aluminum-lithium alloys has become an inevitable trend in future aerospace manufacturing. Fusion welding process tests of 6 mm-thick 2195 aluminum-lithium alloy were conducted to study the influence of the trailing shield, types of shielding gas, and welding current on the tensile properties of the joints. The results indicate that the root weld has a good macroscopic appearance and no obvious oxidation when the trailing shield supplied with argon gas is applied. Based on this, when manual argon-arc cap welding is applied, the average tensile strength of the joints reaches 342 MPa, with an elongation after fracture of 4.1% and a joint efficiency of 61.1%. Adding a certain amount of helium to argon or reducing the welding current cannot improve the joint strength. The fracture mechanism of the welded joints is analyzed. It indicates that the liquefied grain boundaries generated in the partially melted zone are the key factors affecting the strength and toughness of the joints. The research results provide data support and theoretical guidance for the welding applications of aluminum-lithium alloys in new-generation rocket tanks.