Abstract: The tribochemical mechanisms of ceramic particle filled polyphenylene sulfide composites sliding against tool steel were investigated by means of scanning electron microscopy and X ray photoelectron spectroscopy. It has been found that the polyphenylene sulfide matrix in the composites filled with SiC, Si 3N 4, Al 2O 3 and Cr 3C 2 underwent tribochemical degradation during the friction process. The degraded products react chemically with counterface Fe and atmospheric O 2, thus generating the compounds such as FeS and FeSO 4 which are helpful in increasing the bonding strength of the transfer film onto the steel substrate. This accounts for the increase in the wear resistance of ceramic particle filled polyphenylene sulfide composites.