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For improving the anti-permeability of waterborne polyurethane coatings to concrete,the silane coupling agent was applied to modify the surface of nano-SiO2 to reduce the reunion degree of nanoparticles,and then the modified nano-SiO2 with better dispersibility was added into the waterborne polyurethane coatings.The modification effect of silane coupling agent on nano-SiO2 was analyzed by thermal analysis (TG),infrared spectroscopy (FT-IR) and dynamic light scattering (DLS),and the effect of nano-SiO2 on the morphology and composition of waterborne polyurethane coatings was also expounded.Furthermore,the influence of nano-SiO2 modified waterborne polyurethane coatings on the anti-permeability of concrete was analyzed.Results showed that the nano-SiO2 modified by silane coupling agent possessed less-OH on the surface and a lower reunion degree.Comparing with the concrete specimens painted with the polyurethane coatings containing no SiO2 or unmodified nano-SiO2,the concrete specimen painted with polyurethane coating containing modified nano-SiO2 had stronger adhesion between the coating and the concrete.The capillary water absorption per unit area of the specimen and the penetration depth of chloride ions were reduced,and the permeability resistance of the concrete was improved.