Abstract: Using an environment-controlled tribometer, the effect of water on friction and wear behaviors of nuclear borosilicate glass were studied by rubbing against a stainless steel ball under various water environments (dry, RH20%, RH50%, RH70%, and liquid water). The experimental results show that the steady-state friction coefficient, wear volume, and the subsurface damage of borosilicate glass substrate decrease with the increasing in relative humidity. Furthermore, in presence of liquid water, the steady-state friction coefficient of glass interface was the lowest among all the cases, accompanying with the lowest wear volume and subsurface damage depth. In dry environments, the wear behaviors of the nuclear borosilicate glass are mainly dominated by adhesive wear and abrasive wear, while it is dominated by water-induced tribochemical reactions when the tests are performed in humid air and liquid water environments. Due to the water-induced tribochemical products and the lubricity of water molecules adsorbed on glass surface, the wear and subsurface damage of the glass in the liquid water are much milder than that in dry and humid environments.