Abstract: The effect of metakaolin (MK) amount (accounting for 20wt%, 30wt% and 40wt% of the total mass of MK/cement mortar) on the passivation film formation and corrosion resistance of passivation film of reinforcing steel in MK/cement mortar was studied by eletrochemical impedance spectroscopy, cyclic potentiodynamic polarization, cathodic polarization, thermogravimetric analysis and diffraction of XRD. The results indicate that the reinforcing steel can form stable passivation film in steel-MK/cement mortar with different MK contents in general environment. In the solution environment of 3.5wt% mass fraction of NaCl, excessive amount of MK reduces the stability of passive film and the corrosion resistance of reinforcing steel in steel-MK/cement mortar. Considering the stability of passive film, the content of MK in cement-based materials should be limited in chloride environment.