Aiming to investigate the effect of welding thermal cycle on microstructure properties of aluminum alloy welded joints in the production process of aluminum alloy carbody,A5083 P-O and A7 N01 P-T4 aluminum alloys were welded separately by using same welding parameters and various welding thermal cycles in same welding environment and constrain condition. The welded joints were analyzed by means of non-destructive examination,metallography and hardness measurement. The test results showed that the A5083 PO and A7 N01 P-T4 had different hot crack tendency,which provided a theoretical basis for multiple repair in the production.