Abstract: The tribological properties of polyacrylate coatings modified by nanometer SiO₂ particles were investigated under water lubrication. The interfacial coalescence between nano-SiO₂ and acrylic resin polymer was characterized by FTIR spectra. SEM was used to characterize the surface abrasion, and the wear mechanism was discussed by assistance of FTIR and abrasion experiments. The results show that chemical bonds exist between SiO₂ and polyacrylate, and the addition of nanometer SiO₂ particles helps to form a lubricating membrane and absorbed water layer under water lubrication, which improves the friction-reduction performance. When the amount of nano-silica is low, the main wear mechanisms of coatings are tribocorrosion abrasion and grain abrasion. As the coating contains 5wt% nanometer SiO₂, the favorable wear-resistance of the coating is obtained, which provides an integrated lubricating membrane and absorbed water layer.