The sliding friction and wear characteristics of a thermoplastic polyimide (PI) were investigated under different PV conditions using a pin-on-disc wear tester. The tribological characteristics of the PI were divided into three wear regions on the basis of the wear degree (slight wear, medium wear and severe wear). The friction coefficient of the PI in slight wear was stable. In the medium wear and severe regions, the friction coefficients of the Pl varied over a wide range, and was unstable. The reason for the variations of friction and wear in the different wear regions was attributed to the rising of PI surface temperature, which led to the variations of the physical state of PI friction surface layer. XPS analysis indicated that carbonation occurred on the friction surface during sliding. It was proved that the reaction product may reduce the friction coefficient.