Graphene oxide (GO) was asymmetric chemically modified with myristyltrimethylammonium bromide (TTAB) to get modified graphene oxide (MGO). This MGO was used as an emulsifier and additive in oil-in-water emulsion. The emulsifying tests showed MGO greatly improved the stability of base emulsion and decreased its droplets size. Tribological test results showed that under the boundary lubrication condition with MGO-emulsion, the friction coefficient (COF) and the wear rate of the steel ball were decreased by about 18% and 48% respectively, comparing with base emulsion lubrication. The tribological mechanism of MGO-emulsion could be explained by the strong film-forming ability on the metal surface; the good lubricity of its small droplets; the formed adsorption film, transfer film and tribofilm between the contact surfaces.