Abstract: The surface of nano-TiO₂ was modified by coupling agent in this paper.The modified and unmodified nano-TiO₂ were added into to the polyurethane to prepare nano-composite coatings.The results indicated that the modified nano-TiO₂ disperse well in the coatings,The saline immersion resistance of nano-composite coatings was improved effectively.When the content of modified nano-TiO₂ was 3%,the saline immersion resistance of coatings was the best.After 56 days aline immersion,the pencil hardness of composite coatings with 3% modified nano-TiO₂ decreased from 3H to HB,the adhesion rank decreased from 1 to 3,the glossiness was from 120.9 to 99.6,and anti impact properties decreased from 22N·cm to 12N·cm.The reduction of properties is the smallest in all of samples.