For an concave cross-section aluminum alloy ring with an outer diameter of Φ350 mm, two different ring blanks were designed, and the ring rolling process was numerically simulated by finite element software ABAQUS. Then, the formation process and formation mechanism of shrinkage defects during the rolling process of aluminum alloy rings with concave cross-sections were analyzed by simulation calculations. The results show that the radial shrinkage on the inside of the rings first increases as the ring blank and the mandrel rollers gradually fits together, and then gradually disappears, and the closer the axial shrinkage at the bottom is to the inside, the larger its size is. During the rolling process, the maximum plastic equivalent strain is located in the middle position of the outer surface of the ring, and at the end of the rolling, the plastic deformation is larger in the middle section of the ring, while the equivalent strain in the lower area is smaller. Furthermore, the filling effect, rolling force, and equivalent strain of the two ring blanks were comparatively analyzed. The results show that using the irregular blanks, the parts have better filling effect and smaller axial offset load. Based on the simulation results, rolling experiments are conducted on irregular blanks, and qualified target ring parts are rolled.