Abstract: Candle soot was easily collected. Its surface was negatively charged and so could be readily modified with cationic surfactant cetyltrimethyl ammonium bromide. The morphology was characterized through high resolution transmission electron microscopy, which indicates that candle soot was constituent of onion like nanoparticles with relatively uniform diameter of 20 nm and good dispersivity. The dispersion stability of candle soot in liquid paraffin was significantly improved. The tribological properties of candle soot before and after modification in liquid paraffin were obtained on an Optimal SRV-IV oscillating reciprocating friction and wear tester. The results show that bare candle soot as an additive made no improvement on the lubricity of liquid paraffin. However, surfaced modified candle soot dramatically reduced friction and wear of sliding pairs. The lubricating mechanism was proposed through characterization of wear scars by scanning electron microscope, in-situ Raman spectroscopy and X-ray photoelectron spectroscopy.