Partially sintered zirconia ceramics (PSZC) were prepared via isostatic pressing and partially sintering，with zirconia nanopowder as the raw materials. PMMA-Zirconia organic-inorganic composites were prepared by vacuum infiltration of the prepolymerized MMA into the PSZC, followed by in-situ polymerization. The results show that prepolymerized MMA immerged fully into the open pore of PSZC and polymerized. When the relative density of PSZC is within the range of 63%～82%, the composites have a three-point bending strength of 154～287MPa, fracture toughness of 3.68～4.81MPa·m^1/2 ,which are much higher than those of PSZC. The composites can be machined by dental CAD/CAM system to manufacture dental restoration.