Abstract: Polybenzoxazines (PBz) have attractive properties, such as low water absorption, near-zero cure shrinkage rate and good dielectric properties. Recently, the potential application of polybenzoxazines as anti-corrosive coating gradually attracted the researchers' attention. Silanes gradually replaced traditional pretreatment technologies on surface of metal like chromates and phosphate passivation because of their nontoxic and environmentally friendly characteristics. Using silane as organic coating components can efficiently improve the anti-corrosive performance. A main-chain-type benzoxazine precursor (Bz) was prepared using bisphenol A, 4, 4'-diaminodiphenylmethane and paraformaldehyde. γ-Mercaptopropyl trimethoxysilane (KH590) modified main-chain-type polybenzoxazine coatings (PBz/KH590) were prepared on the mild steel by roller painting and thermal curing method. Corrosion resistant performance of PBz/KH590 coating was studied by electrochemical impedance spectroscopy (EIS) measurement. The results demonstrate that the modification of KH590 enhances the compactness of PBz/KH590 coating and thus the impedance of the coating is also increased, leading to a promotion of its anti-corrosive performance. When m(KH590):m(Bz)=40:100, the PBz/KH590 coating exhibited optimum corrosion resistant performance with an impedance of 6.29×10⁸ Ω·cm² at 0.01 Hz, which is 5 orders of magnitude higher than that of bare mild steel.