Abstract: Blue fluorescent liquid carbon dots (C dots) with alkyl chains coated on the surface were obtained by simply refluxing oleylamine in chlorobenzene followed by purification through silica gel column chromatography. High-resolution transmission electron microscope (HR-TEM), Fourier transform infrared spectrum (FT-IR) and fluorescence spectrum proved the successful preparation of alkylated, blue-emitting C dots. Differential scanning calorimeter (DSC) proved the liquid character of the C dots at room temperature. The C dots showed good compatibility with paraffin oil and the mixture exhibited long-term stability. The effect of the amount of C dots on friction reduction and anti-wear of paraffin oil was studied. Both the friction coefficient and wear volume of the mixture with 0.1% C(weight fraction) dots were lower than that of pure paraffin oil. When the amount of C dots reached 1.0%(weight fraction), the minimum friction coefficient was obtained. The good performance of C dots in improving the anti-friction and anti-wear effect of paraffin oil was due to the formation of a layer of carbon and a layer of iron tetroxide.