Abstract: A reciprocal friction and wear tester was performed to investigate the effect of biomass fuel soot and diesel oil soot on the friction and wear behavior of cast iron/cast iron pair under dry sliding condition. The tribological mechanisms of the two kinds of soot were analyzed with the assistance of scanning electron microscopy,atomic force microscopy and Raman spectrometry. Results show that the introduction of the two kinds of soot contributed to significantly reducing the friction and wear of the cast iron/cast iron pair under dry sliding condition. Both friction coefficient and wear mass of the frictional pair increased with the increase of reciprocal frequency. And diesel oil soot was superior to biomass fuel soot in terms of the friction-reducing and antiwear abilities. This is attributed to the mechanical properties and self-lubricity of the soot as well as the surface properties of the frictional pair,which mainly involved the formation of soot-containing film on sliding surfaces,the friction-induced generation of iron oxides and the increase in the content of ordered carbon on sliding surfaces.