Studies on the sintering, microstructure, mechanical properties and low temperature degradation behavior of yttria stabilized-tetragonal zirconia polycrystal (3Y-TZP) were carried out. The results show that the addition of Al2O3 and MgO improve the sintering at low temperatures, and cause exaggerated grain growth and the transformation of tetragonal-ZrO2 to monoclinic-ZrO2 with corresponding changes in the mechanical properties. The addition of the yttria-free monoclinic zirconia particles change the overall yttria distribution and induce an active transformation toughening mechanism. Furthermore, the dispersed yttria-free ZrO2 can inhibit the tetragonal zirconia transformarion, which is beneficial to the improvement of the low temperature degradation behavior of 3Y-TZP ceramics.