Phenylethynyl-terminated polymerization of monomer reactant thermosetting polyimide (PI) was synthesized, and the PI/SiO2 nanocomposite films were prepared via in situ polymerization of monomer with the nano-SiO2 particles. Analysis indicated that the surfaces of the nano-SiO2 slightly react to the PI, and nano-SiO2 was homogeneously dispersed in the PI at low filling content while agglomerate was a presence of high filling content. Thermogravimetric analysis showed that the decomposition temperatures of the PI/SiO2 nanocomposites were increasing as the increasing of filler contents when the nano-SiO2 content was below 9 wt %, but it showed a decreased tendency when it was above 9 wt %. Tribological studies showed that the nano-SiO2 contributed to the significant decreasing of the friction coefficient and wear rates of the PI at dry sliding condition of low filler content, and the PI/SiO2 nanocomposites could be promising material used as tribomaterial in dry sliding condition against GCr15 steel. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012