The invention discloses an on-site repair welding method for a 5A06 aluminum barrel finished product welding joint stress corrosion crack, and belongs to the technical field of aluminum alloy structural member welding. The on-site repair welding method for the 5A06 aluminum barrel finished product welding joint stress corrosion crack can achieve product defect on-site repair without separating an aluminum barrel from a lathe with a high qualified rate. According to the technical scheme, the on-site repair welding method for the 5A06 aluminum barrel finished product welding joint stress corrosion crack comprises the following steps that 1 the repair welding method is selected, a welding technological parameter is determined, and a destressing mode and a technological parameter are determined; 2 the type and the size of a groove needing repair welding are determined, and a welding groove is prepared; 3 repair welding is conducted with the selected welding technological parameter; 4 a hammer is adopted for hammering a surface-layer welding joint of the repair-welding welding joint for destressing; and 5 liquid penetrant test is adopted for assisting in checking whether the repair-welding surface of the welding joint has the crack or not. The on-site repair welding method for the 5A06 aluminum barrel finished product welding joint stress corrosion crack is mainly used for conducting defect on-site repair for the 5A06 aluminum barrel finished product without separating the aluminum barrel from the lathe.