The friction and wear behaviors of UHMWPE and its composites filled by carbon fiber and glass fiber respectively were investigated by a selfdesigned friction test,by which the deep sea environment was simulated.The influence of seawater hydrostatic pressure on seawater absorption,chemical stability and plastication effect was further studied.The results show that hydrostatic pressure significantly increases the friction coefficient of the hydrodynamic region,while it has little influence on that of the boundary lubrication region.After saturated in seawater under specific hydrostatic pressure,the wear rate of UHMWPE and its composites is increased.The decreased antiwear performance is possibly a combined effect of increased seawater absorption,damaged chemical stability and accelerated plastication effect.Both carbon fiber and glass fiber can improve the antiwear performance of the UHMWPE matrix.The wear rate of the composite filled by carbon fiber is almost unaffected by the applied hydrostatic pressure,which is much lower than that of the composite filled by glass fiber.