Abstract: The friction and wear behaviors of glass fiber and carbon fiber reinforced MC nylon composites (coded as GF/MCPA and CF/MCPA, respectively) under water lubrication were investigated with an MM 200 friction and wear tester. The worn surfaces and wear debris were observed and analyzed using a scanning electron microscope and a surface profilometer. The results show that fiber reinforced MC nylon composite sliding against AISI1045 steel under water lubrication registers lower friction coefficients than under dry sliding and the wear resistance of the reinforced composites is better than that of MC nylon matrix. Of the two composites, CF/MCPA has smaller friction coefficient and higher wear resistance than GF/MCPA. This is attributed to the formation of a uniform and continuous transfer film on the counterpart steel surface sliding against CF/MCPA. CF/MCPA is characterized by adhesion and transfer, accompanied by slight plowing in sliding against steel, while GF/MCPA is characterized by micro cutting.