Chloride induce corrosion destroys the structure of marine concrete, thereby shortening its actual service life. In this study, Fe-based layered double hydroxides (LDHs), including CaFe-NO3 and CaFeAl-NO3 LDHs, and polyvinylpyrrolidone (PVP), were added to increase the anti-corrosion property of mortar. Electrochemical tests and chloride penetration resistances of the samples were conducted, and the corresponding micro-mechanisms were investigated. The samples that were immersed short-term (5 d) exhibited similar electrochemical characteristics and corrosion tendencies compared to the 7 d samples. With increasing immersion time, all the samples were corroded, whereas the LDHs-PVP composites still exhibited higher resistances and impedance, larger arc radius, and a lower corrosion current density and corrosion rate than the other samples due to the synergistic effect via the formation of a passive film by PVP, the increased compactness and adaptability by Fe-based LDHs, and promotion of uniform dispersion of LDHs in slurry by PVP. Further, the work function of the LDHs-PVP composites was lower than that of the control, indicating that the addition of LDHs and PVP decelerated the corrosion reaction of steel. Thus, the LDHs-PVP composites exhibited high anti-corrosion property; the rapid chloride migration coefficient and total charge passed decreased by 17.5% and 4.9% compared to those of the control, respectively, highlighting the potential of this composite as effective inhibitors for marine concrete corrosion.