Surface aluminizing for magnesium alloy is an effective method to improve corrosion resistance. This research introduces surface nanocrystallization as the pre-process of aluminizing. AZ91D magnesium alloy is processed by high energy shot peening (HESP) to achieve surface nanocrystallization, and then vacuum solid state aluminum diffusion to obtain aluminized layer. The morphology of the aluminized layer is observed with Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM). It shows that the surface of the nanocrystalline grain size of 100 nm was obtained after HESP of AZ91D magnesium alloy. After HESP, the depth of the aluminized layer is thicker than that of the aluminized layer without HESP. After diffusion of 12 hours under the temperature of 440 ℃, the depth of aluminized layer increases to 70 mm. The corrosion resistance of AZ91D magnesium alloys are characterized by electrochemical method. It shows that the aluminized layer obviously decreases the corrosion rate of AZ91D magnesium alloy. Therefore, high energy shot peening(HESP)was beneficial to surface aluminizing and can improve the corrosion resistance of magnesium alloy.