The EIS on the anodic process of pure Zn in an alkaline solution were performed and fitted using the expression of Faradic admittance, based on which the mechanism of the process was proposed. The results showed that besides electrode potential E the electrochemical reaction rate was affected by the adsorption of Zn(OH)ads on the electrode surface and the diffusion of in the electrolyte in active region, and only by the covering of passivation layer on the electrode surface in both transitive and passivation regions. The equivalent circuits applied in these various circumstances were proposed and the variation of some parameters and state variables was also discussed.