Abstract: Aluminum-copper alloy 2219 and aluminum-lithium alloy 2195 serve as materials for aerospace storage tanks. After friction stir welding, the joint strength between these dissimilar materials shows significant reduction compared to 2195 base metal. To enhance the mechanical properties of dissimilar welded joints and clarify the relationship between material configuration sequence and joint strength, the effects of heat treatment processes on joint microstructure and mechanical properties were investigated. Using welding parameters of 200 mm/min travel speed and 800 r/min rotation speed, friction stir welding experiments were conducted on 2195-T8 and 2219-T6 alloys with opposing material configurations. Comparative analysis revealed that dissimilar welded joints with high-strength 2195 alloy positioned on the advancing side(AS) demonstrated superior mechanical performance. The 2195AS/2219RS dissimilar joint exhibited 23% higher tensile strength compared to 2219 homogeneous joints. To further improve joint strength, solution treatment and aging processes were applied to 2195AS/2219RS dissimilar joints. The results indicated that heat treatment at 535 ℃ for 1 hour followed by 165 ℃ aging for 12 hours achieved optimal joint strength, with yield strength and tensile strength increasing by 65% and 36% respectively compared to as-welded condition, significantly enhancing deformation resistance. However, post-treatment observations showed grain coarsening in the weld nugget zone and evident brittle fracture characteristics in fracture surfaces.