The insufficient lubrication caused by the low viscosity of water has greatly limited the application of waterlubricated bearing, especially under the conditions of heavy load and low speed. In order to solve this problem, a composited strategy is proposed by using the hydration lubrication of polyacrylamide (PAAm) hydrogel to improve the tribological performances of UHMWPE. The PAAm hydrogel microspheres were synthesized by emulsion polymerization, and the PAAm hydrogel microsphere/UHMWPE composites were prepared by melt blending method. The effects of particle size, crosslinking density and filling content of PAAm microspheres on the tribological performances of the composites were tested and analyzed. The results show that the PAAm fragments can form a hydration lubrication layer and improve the tribological performances of the composite. The design of PAAm microsphere/UHMWPE composite provides a novel method to develop high-performance materials for water-lubricated stern tube bearing.