<p>The early stages of corrosion in AZ31B magnesium alloy frame parts are highly dependent on the surface condition of the material, and milling parameters play a critical role in influencing the surface quality. To improve the surface quality of magnesium alloy after milling and enhance its corrosion resistance, response surface methodology (RSM) was used to conduct milling and electrochemical corrosion tests on AZ31B magnesium alloy. A predictive model was established between milling parameters and various response objectives, and its accuracy was verified through analysis of variance (ANOVA). This research innovatively explored the impact of milling parameters on the corrosion resistance of magnesium alloy and optimized the milling parameters to achieve the optimal surface quality and corrosion rate. The results show that the corrosion performance of AZ31B magnesium alloy frame parts is closely linked to the variation in surface roughness. Increasing the spindle speed improves the corrosion resistance of the material, while an increase in feed per tooth and milling depth leads to higher surface roughness, which exacerbates corrosion of the machined surface. The surface roughness and hardness of the machined surface initially increase and then decrease with higher spindle speed, while both parameters increase with rising feed per tooth and milling depth. Under the optimized milling parameters, the errors between predicted and experimental values for corrosion rate, surface roughness, and surface hardness were kept low, at 12%, 5.18%, and 3.48%, respectively, fully demonstrating the model’s validity and practical value in production.</p>