Purpose Ultra-high molecular weight polyethylene (UHMWPE) is adopted in water-lubricated bearings for its excellent performance. This paper aims to investigate the tribological properties of UHMWPE with a molecular weight of 10.2 million (g mol(-1)) under different molding temperatures. Design/methodology/approach The UHMWPE samples were prepared by mold pressing under constant pressure and different molding temperatures (140 degrees C, 160 degrees C, 180 degrees C, 200 degrees C, 220 degrees C). The friction and wear tests in water were conducted at the RTEC tribo-tester. Findings The friction coefficient and wear loss decreased first and rose later with the increasing molding temperature. The minimums of the friction coefficient and wear loss were found at the molding temperatures of 200 degrees C. At low melting temperatures, the UHMWPE molecular chains could not unwrap thoroughly, leading to greater abrasive wear. On the other hand, high melting temperatures will cause the UHMWPE molecular chains to break up and decompose. The optimal molding temperatures for UHMWPE were found to be 200 degrees C. Originality/value Findings are of great significance for the design of water-lubricated UHMWPE bearings.