The 7003 aluminum alloy commonly used in battery packs was taken as the research object. After joint welding by CMT (cold metal transition welding) process, the structure and performance were studied after heat treatment with solid solution at 485 ℃ for 3 h, artificial aging at 160 ℃ for 2 h and natural aging for 72 h. The corrosion resistance, mechanical properties and microstructure of the base material and weld of the aluminum alloy joint were studied and analyzed by means of slow strain rate tensile test, normal temperature tensile test, micro-vickers hardness, scanning electron microscope and other analytical methods. The results showed that when the slow strain rate was 1×10-6 s-1, the stress corrosion sensitivity index of the substrate was 2.73%, the welding sample was 9.74%, while the intergranular corrosion of the welded joint samples was level 4 and peeling corrosion rating was PA. The conductivity, tensile strength and elongation of the joint were 22.0% (IACS), 330.7 MPa and 10.0% respectively.