In this research, the tribological characteristics of PEEK filled with short carbon fiber/PTFE/Graphite sliding against AISI630 stainless steel under water lubrication were investigated. The friction experiments were conducted on MCF-10 ring-on-ring test rig. Based on SEM analysis of worn surfaces, an attempt was made to approach the tribological mechanism of friction pairs. The results showed that the matching materials achieved the best tribological performance at velocity of 1 m/s and load of 1.66 MPa. When load applied on the specimens was increased to 2.49–3.32 MPa, cracks and delamination wear occurred in the surface of PEEK. The effect of sliding velocity on triobological performance of matching materials was complicated. At higher sliding velocity, hydrodynamic lubrication was easier to form. However, the rapid rising temperature with the increase of sliding velocity had adverse effect on water lubrication film. Under load of 1.66 MPa and sliding velocity of 1.5–2 m/s, adhesive wear was the dominant factor in the sliding process. The matching materials performed higher friction coefficient and wear rates under insufficient water lubrication than that under circulating water lubrication. It is attributed to that the friction heat accumulated gradually. The research results will lay the foundation for the materials screening of key friction pairs in the water hydraulic components.