Barrel-shape is a common phenomenon of non-uniform deformation generated in the conventional upsetting process of cylinder. In order to improve the uniformity of upsetting, taking a 6061 aluminum alloy cylinder of Φ4.08 mm×4.8 mm as the experimental object, the ultrasonic-assisted multi-step upsetting process was adopted, namely, ultrasonic-assisted upsetting was performed first, and then conventional non-ultrasonic upsetting was continued to obtain the anti-barrel-shape intermediate and the final near-cylindrical body of Φ5.4 mm×2.8 mm respectively. The experiments and the FEM simulation research indicate that the anti-barrel-shape intermediate formed by ultrasonic-assisted upsetting can show an approximately elliptical curve or hyperbola profile, and at the same time, the formation of anti-barrel-shape profile promotes the radial deformation of the end face for cylindrical specimen. In addition, ultrasonic-assisted multi-step upsetting can promote an approximately uniform distribution of equivalent plastic strain in the specimen, thereby improving the uneven deformation of barrel-shape. The shear strain generated in the anti-barrel-shape specimen can be superposed with the shear strain caused by conventional non-ultrasonic upsetting in the subsequent section to create a counteracting vector. The shear strain offset mechanism promotes the uniform deformation of the entire cylindrical specimen.