(Y, Nb)-TZP with a composition of 90.24 mol% ZrO2-5.31 mol% Y2O3-4.45 mol% Nb2O5 and (Y,Nb)-TZP/Al2O3 composite were sintered for 2 h at 150$0^{circ}C$ and subsequently isostatically hot pressed for 0.5h at 150$0^{circ}C$ under 100 MPa in argon gas to evaluate mechanical properties of (Y,Nb)-TZPs prepared by different methods Regardless of preparation methods no monoclinic ZrO2 phase was observed for specimens after annealing for 20 h at 18$0^{circ}C$ under 3.5 MPa water vapor pressure indicating that specimens are stable under autoclave conditions. The optimized mechanical properties of the sintered (Y,Nb)-TZP/Al2O3 composite and the HIPed (Y,Nb)-TZP/Al2O3 composite were observed when 30vol% of 2.8${mu}{ extrm}{m}$ Al2O3 was added respectively. The optimized strength and fracture toughness of the HIPed (Y,Nb)-TZP/Al2O3 composite were 944 MPa and 9.9MPa.m1/2 respectively. The increase in fracture toughness of the composite is likely attributed to the combined effects of grain bridging crack deflection and Kres/R-curve toughening