<p>The appropriate rim wall thickness is of great significance for the back extrusion process of the magnesium (Mg) alloy wheel. Currently, the rim wall thickness of plastic-formed Mg alloy wheels is mostly based on that of casting aluminum (Al) alloy wheels, resulting in a low wheel yield. This paper analyzed the effect of different rim wall thicknesses on the process of Mg alloy wheels by establishing the numerical model of Mg alloy wheels. The study discovered that as the rim wall thickness increases, the filling rate at the rim slows down, accompanied by a lower effective strain and strain rate. The lower strain rate leads to a decrease in the deformation resistance of the billet, and thus, the load required for wheel forming reduces. The reduction in effective strain and strain rate, in turn, leads to a decrease in the deformation heat during the wheel-forming process. An appropriate increase in the rim wall thickness can reduce the deformation heat at the spokes, thereby refining the grains of the spokes. If the rim wall thickness is increased excessively, the overall dynamic recrystallization (DRX) of the wheel will not be promoted, resulting in coarse grains. Within the scope of this study, the best microstructure distribution was obtained when the rim wall thickness was increased by 14.3% from the current rim wall thickness. The damage factor at the upper rim shows a trend of increasing first and then decreasing with the increase in the rim wall thickness. The cracking tendency is the greatest when the rim wall thickness is increased by 28.6% on the current basis. For comprehensive consideration, the more optimal rim wall thickness is increased by 14.3% on the current basis.</p>