The tribological behaviors of polyimide（PI）polymer reinforced with different volume content of carbon fiber(CF) in seawater lubrication were studied by using seawater resistant MCF10 test rig.The worn surface morphology of PI composites was observed by scanning electron microscope (SEM) for analyzing the wear mechanism of PI material.The results show that CF can effectively improve the wear resistance of PI polymer in seawater.With the increasing of CF content,the wear resistance of PI composite is firstly increased and then decreased,and it has the best wear resistance when CF content is 20% in volume.This is mainly because that CF can bear a large proportion of contacted load in the process of friction,inhibiting the further wear of PI composite.The additive CF enhances the scratch and plough effect of PI composites on coupling surface,leading to the increase and a larger amplitude of oscillation of friction coefficient,while the CF content has little influence on the friction coefficient of PI composite.The main wear mechanism of pure PI material is shown as adhesive wear and mechanical plough,and that of CF reinforced PI polymer is abrasive wear of matrix and grind and fracture of CF.