Taking the rotating extrusion process of a magnesium alloy inner rib shell as the research object, based on the problem that the actual deformation of blank in the rotating extrusion can not be synchronized with the feeding speed controlled by the device,the numerical simulation of rotating extrusion process for inner rib shell of magnesium alloy was conducted by the rigid-plastic finite element method, and the independent and compound influences of different punch height-to-diameter ratios and feeding speeds on the forming precision of inner ribs shell were compared and analyzed. Finally, the functional relationship between the two factors on the forming precision of inner rib shell groove is obtained, and the forming scheme that ensures the forming accuracy is determined, i.e., the displacement deviation of punch could be controlled at a lower level when the height-to-diameter ratio of punch is 1 and the feeding speed is 0.5 mm·s-1. Furthermore, the physical experiment was conducted on the 6300 kN-13.5 kN·m multi-direction loading rotating extrusion tester developed by North University of China. And the experimental results are basically consistent with the simulation results.