ZrO2-Toughened Alumina-Ceramics (ZTA) with SiC Whisker as dispersive additive were prepared by pressureless sintering at 1$600^{circ}C$ and 1$650^{circ}C$ and by HIPing at 1$600^{circ}C$ in Ar atmosphere. Effects of SiC-Whisker addition on microstuructural, mechanical, and thermal properties were investigated and the toughening mechanisms between theory and experiment were compared. Specimens with 15 vol% Whisker prepared by HIPing showed 8.26 MPa.ma1/2 in fracture toughness and 600 MPa in flexural strength owing to contribution of the three mechanisms such as crack deflection, whisker bridging and whisker pullout in spite of difference between the theoretical and experimental values due to the partial inhomogeneous dispersion of SiC-Whisker in the matrix and the processing flaw.