Abstract: The thickness，resistivity and degree of pore saturation of concrete cover have significant influences on the corrosion mechanism and corrosion rate of steel bar embedded in concrete． The influences of the thickness，resistivity and degree of pore saturation of concrete cover on the corrosion mechanism and corrosion rate of steel bar were investigated quantitatively，based on the macro-cell corrosion model of steel bar． The results show that the thickness and degree of pore saturation of concrete cover significantly affect the corrosion mechanism and corrosion rate of steel bar corrosion． If the corrosion of steel bar is under the control of resistivity，the corrosion rate diminishes with the increase of resistivity and accelerates with the increase of cover thickness，while the degree of pore saturation of concrete cover has negligible effect． When the cathodic reaction prevails，however，the corrosion rate decelerates with the increase of the degree of pore saturation and thickness of concrete cover while the effect of resistivity can be neglected．