The thermal fatigue behavior of alumina ceramics was investigated by water quenching method. Single-quench thermal shock tests were performed to decide the critical thermal shock temperature difference ($Delta$Tc) which was found to be 225$^{circ}C$ Cyclic thermal shock fatigue tests were performed at temperature diff-erences of 175$^{circ}C$, 187$^{circ}C$ and 200$^{circ}C$ respectively. After cyclic thermal shock fatigue test the distributions of retained strength and crack were observed. Retained strength was measured by four point bending method and crack observation method bydye penetration. In terms of the retained strength distribution the critical number of thermal shock cycles(Nc) were 7 for $Delta$T=200$^{circ}C$, 35 for $Delta$T=187$^{circ}C$ and 180for $Delta$T=175$^{circ}C$ respec-tively. In terms of the crack observation the critical number of thermal shock cycles were 5 for $Delta$T==200$^{circ}C$ 20 for $Delta$T==187$^{circ}C$ and 150 for $Delta$T=175$^{circ}C$ respectively. The difference of Nc investigated by two different methods is due to the formation of the longitudinal cracks which had no effect on the four point bending strength. Therefore the thermal fatigue behavior of alumina ceramics could be more accurately described by the crack observation method than the retained strength measurement method.