Abstract: Hydrophobic nano-SiO₂ particles were prepared by surface modification，and the diameter of nano-SiO₂ was about 50 nm.Nano-SiO₂ composite coating was obtained by adding nano-SiO₂ particles into the polyurethane varnish through mechanical agitation and ultrasonic dispersing.Linear sweep voltammetry，electrochemical impedance spectroscopy（EIS）and mass loss measurements were used to evaluate the anti-corrosion property of the nanocomposite coating in NaCl solution.The results showed that the corrosion resistance of nano-composite coating was improved by adding modified nano-SiO₂ particles.The anodic corrosive current of nanocomposite coating was decreased by about 1 order of magnitude，and the corrosion rate of nanocomposite coating was about 20%—70% lower than that of the original polyurethane varnish.In addition，the adhesion of nanocomposite coating was improved by adding modified nano-SiO₂ particles.The influence of nano-SiO₂content on the performance of nanocomposite coating was also discussed.