The friction coefficient of carbon nanotube reinforced the nitrile composites under water lubricated condition was investigated using a ship propeller bearing friction tester at different condition. The mechanical properties of the composites were also tested. The results showed that CNTs could improve the mechanical properties and reduce the friction coefficient of nitrile rubber considerably under water lubricated conditions, due to the effective reinforcing and self-lubricating effects of CNTs on the nitrile matrix. With the increasing pressure, the friction coefficient of the nitrile/CNT nanocomposites decreased under the water lubricated condition, which is because that the surface deformation of the nanocomposites was in favor of the water films forming. However, with the increasing temperature of water, the friction coefficient of the nitrile/CNT nanocomposites increased under water lubricated condition, owing to the thinner operating film and the increasing real contact area.