<p>During the hot spinning process of aluminum alloy tube parts, it is easy to have the phenomenon of inner diameter expansion, which makes it difficult to guarantee the dimensional accuracy of the tube. For a better understanding of the mechanism and to find a way to solve this problem, the finite element numerical simulation method was applied to systematically study the relation of stress and strain evolution with the inner diameter expansion, and the quantitatively influence of the spinning process parameters including feed speed, rotation speed, thinning rate, and spinning temperature on the inner diameter expansion data. The results show that during the spinning process, there is a line with the same three-dimensional principal stress in the radial direction of the tube in the contact area between the roller and the tube, which is the plastic flow boundary of the material. The contact area is divided into two regions by the dividing line. The stress state of these two regions is three-dimensional compressive stress, but the different flow directions of the two regions lead to the inner diameter expansion. The change of spinning process parameters affects the size of the inner diameter expansion by affecting the position of the plastic flow boundary. Within a reasonable range, the smaller the feed speed, thinning rate, and spinning temperature, the higher the rotation speed, the closer the boundary position to the unformed area of the tube, and the smaller the inner diameter expansion of the tube. The achievement of this study has certain theoretical guiding significance for selecting appropriate process parameters to control the inner diameter expansion amount to improve the dimensional accuracy of spinning forming tube.</p>