Ultra-high molecular weight polyethylene (UHMWPE) has great potential in the field of water-lubricated bearings. However, water-lubricated bearing made of pure UHMWPE produce significant heat and undergo physical damage under low speed and heavy load conditions. These performance issues can be improved by reinforcement with fibers that have excellent complementary properties to UHMWPE. Polyester fibers (PETFs) have high compressive strength and wear resistance, and corresponding oriented-fiber-reinforced-composites (OFRCs) wherein PETF acts as reinforcement show even better mechanical and tribological properties. In this study, the influence of PETF density on UHMWPE was investigated by systematic testing of different OFRCs. The results show that the optimal fiber density of composites with PETF oriented along the axial direction was between 1.1 wt% and 2.2 wt%, and that for heavy loads, performance deteriorated with increasing fiber density. Compared with UHMWPE, OFRCs with the optimal fiber density obtained from this study reduced friction coefficient by up to 25.93 % and wear volume by 22.67 %, respectively. Considering the low cost, high durability, and relatively low content (<2.2 wt%) necessary for enhanced properties, reinforcement with oriented PETF is a viable approach to enhance water lubrication performance of UHMWPE.