Abstract: Weld quality and mechanical properties of A356 casting and 6082 profile in three different processes were studied and the fatigue mathematical model of weld was established through dynamic fatigue test. Mechanical properties and weld quality of welded samples of A356 castings and 6082 profiles were studied through weld penetration, mechanical properties and dynamic fatigue test. The result showed that welding quality of A356 castings and 6082 profiles was qualified. Mechanical properties and fatigue life of welded samples both decreased. When A356 castings and 6082 profiles were welded with 3～5 mm wall thickness, it was recommended for MIG that welding current was 160 A, welding speed was 0.15 m/s, and the pulse correction was 1%.Highlights: (1) The welding parent metal was A356 aluminum casting and 6082 aluminum profile. There were few related reports in domestic and foreign literature.(2) Taking split-type welded aluminum alloy automobile chassis parts as the research object, it provided a benchmark for the automotive field of lightweight, precision and integration.(3) Based on the welding process of aluminum alloy at home and abroad, the best welding process parameters of thin-walled aluminum alloy (wall thickness 3～5 mm) were obtained by test method, which provided reference for the domestic and foreign counterparts.