In this study, the Fe3O4@PEG nanocomposites with core-shell structure were fabricated by a co-precipitation method and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometer and thermal gravimetric. The physicochemical and tribological properties of the Fe3O4@PEG nanocomposites in aqueous glycerol were systematically evaluated on steel/steel contact for the first time. The aqueous glycerol solution added with 1.0 wt% Fe3O4@PEG showed no obvious precipitation after standing for 72 h and had good dispersion stability. Compared with the base aqueous glycerol, the Fe3O4@PEG nanocomposites exhibited excellent friction-reducing and anti-wear properties at an optimal concentration of 1.0 wt%, with a 41.4% decrease in friction coefficient and a 24.1% reduction in wear volume. Also, the Fe3O4@PEG nanocomposites in aqueous glycerol exhibited superior lubricating performance than unmodified Fe3O4. The boundary lubrication films formed on the surface were attributed to be the main factor in reducing friction and wear, and a possible lubrication mechanism was suggested.