The full exfoliation graphene oxide (GO) nanosheets were synthesized by an improved Hummers' method. The phenylethynyl terminated thermosetting polyimide (PI) and PI/GO nanocomposites were prepared via a polymerization of monomer reactants process. Thermogravimetric analysis indicated that the incorporation of GO increased the thermal stability of the PI at low filling content. The friction and wear testing results of the PI and PI/GO nanocomposites under dry sliding condition against GCr15 steel showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The friction and wear properties of the PI and PI/GO nanocomposites were investigated on a model ring-on-block test rig under dry sliding conditions against the GCr15 steel. Experimental results showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The optimum GO content of nanocomposite for tribological properties is 3 wt%, which could be a potential candidate for tribo-material under dry sliding condition against GCr15 steel.