The work aims to improve saline water resistance of polyurethane(PU)/Al-Sm2O3 composite coatings. PU/Al- Sm2O3 composite coatings were modified with sericite and silane coupling agent KH550, and varying patterns of microstructure, infrared emissivity, near-infrared reflectivity and mechanical properties of the coatings before and after modification were systematically investigated, then the causes were analyzed and discussed. Compared with the unmodified coatings, microstructure of the modified sericite and KH550 coatings was almost unchanged after corrosion, and the modified coatings had lower near-infrared reflectivity of 1.06 μm and better mechanical properties under the same corrosion conditions of saline water. Hardness, adhesion strength and impact strength of the modified coatings were maintained at 3H, grade 1 and 50 kg?cm 10 days after saline water corrosion. Sericite and KH550 modification can improve the stability of low near-infrared reflection property and mechanical properties of PU/Al-Sm2O3 composite coatings to saline water corrosion.