Microstructure and mechanical properties of CeO2/Y2O3/ZrO2 ceramics were investigated using ultrafine CeO2/Y2O3/ZrO2 powder as the starting material. The structures of CeO2/Y2O3/ZrO2 containing 8~12mol% CeO2 were composed of tetragonal phases. They exhibited an extremely high bending strength (950 MPa) and fracture toughness (12MPa·m1/2). The structural details of CeO2/Y2O3/ ZrO2 were studied by TEM, SEM and XRD. The effects of the structure on mechanical properties were discussed. Plungers and ball valves by the CeO2/Y2O3/ZrO2 ceramics have higher wear resistance and corrosion resistance than metal. Their service life is about 6 ~ 10 fold more than that of metal.