Reduction of friction and wear is a key aspect in saving materials and energy of moving components. The tribological mechanism response for the ultralow frictional behaviors should be paid enough attention. In the
present work, the polyimide (PI) composites were obtained by in-situ adding with multiwalled carbon nanotubes (CNTs). It is disclosed that the incorporation of CNTs enhanced the strength, modulus and hardness of PI matrix. Besides, in tests with sliding against bearing steel (GCr15) surface, PI composite adding with only 1.0 wt.% of CNTs exhibited the ultralow low friction coefficient (0.05) and specific wear rate (1.0×10−6mm3/Nm), which were reduced by 90.7 % and 82.0 % compared to pure PI, respectively. Comprehensive characterization evidenced that a nanostructure tribofilm comprising carbon nanospheres and graphene nanosheets was established when sliding occurred with PI composites due to the tore and unwrapped of CNTs released onto the sliding interface. It was believed that the digest CNTs and tribo-chemical products continuously fed into the tribofilm enhanced its lubricity and load carrying capacity. Moreover, this work provides a strategy for developing highperformance polymer-on-metal sliding pairs with regard to reducing friction and wear through tailoring interface nanostructures.