The tribological properties and lubricating mechanisms of carbon fiber/polytetrafluoroethylene(CF/PTFE) and glass fiber/polytetrafluoroethylene(GF/PTFE) composites were investigated when paired with silicon nitride ceramics in a seawater environment.The effects of sliding velocities on the friction and wear performances were analyzed.The results show that the tribological properties of PTFE,CF/PTFE,GF/PTFE materials paired with Si3N4 ceramics are significantly improved with the increase of sliding velocities in a seawater environment,and the friction coefficient and wear rate show a significant decrease trend.CF/PTFE composite exhibits superior tribological properties,with a friction coefficient as low as 0.026 at a sliding velocity of 1 000 r/min.The characterization results of the worn surface indicate that PTFE based composite materials generate a lubricating film during the friction process due to tribochemical reaction in a seawater environment,which can provide good lubrication and wear reduction effects for the friction pair,thereby reducing the occurrence of friction and wear behavior.