Through first-principles calculations, we proposed two main parameters of Esurf/ρ (ρ=N/S) and work function Ф to explain the mechanism of corrosion resistance of different crystallographic orientations of the same metal or alloy, and found these two parameters together play important roles in determining the anodic dissolution behaviors.Through our model, we studied the corrosion resistance of different crystalline planes of Mg-based alloys, and derived that the anodic dissolution rates of the prism crystallographic planes (11-20) and (1-100) are about 1.48~9.38 times higher than that of the basal plane (0001).This fact interpreted well the experimental observations.Moreover,the alloying addition of Al or Zn in Mg results in the fact that Mg is positively charged whereas Al or Zn is negatively charged.Hence, Al accelerates Mg dissolution, and also enhances the formation of hydride.However, the 1 wt.% Zn alloying addition effectively reduces the anodic hydrogen evolution rate and prohibits the negative difference effect.