The work aims to improve the salt water resistance of polyurethane(PU)/Al composite coating. Graphene modified PU/Al composite coating was prepared by scratch coating method with graphene, PU and Al powders as modification agent, adhesives and pigments, respectively. The variation and causes of microstructure, infrared emissivity, glossiness and mechanical properties of the coating before and after modification by salt water corrosion for different times were discussed. The emissivity stability to salt water corrosion of the graphene modified coating was significantly improved. After salt water corrosion for 21 days, the emissivity was only increased from 0.335 before corrosion to 0.355 after corrosion. After a long period of salt water corrosion, the modified coating had a lower emissivity than the unmodified coating. The modified coating had lower glossiness than the unmodified coating for different salt water corrosion times, and had high stability. After salt water corrosion for 21 days, the glossiness of the modified coating could still be kept at a lower value of 16.1, which was beneficial to achieve compatibility of low emissivity and low glossiness of the coating. The hardness and adhesion strength of the coatings before and after modification had high stability to salt water corrosion. Graphene modification had limited effect on improving the stability of impact strength of the coating to salt water corrosion, and further research and improvement were needed. Graphene modification can significantly improve the stability of infrared emissivity and glossiness to the salt water corrosion of PU/Al composite coating.