The objective of this paper is to investigate the applicability of ultrasonic wave technique to monitor the progress of the thermal shock damage on alumina ceramic. For this purpose, alumina ceramic specimen was heated in the furnace and then was quenched into the water tank. The initiation, growth behaviors of surface micro-cracks as a function of the number of thermal shock cycle have been discussed by taking into account the change of ultrasonic wave velocity and attenuation. The change of both velocity and attenuation of ultrasonic wave showed good relation with the surface crack density changing due to the number of thermal shock cycle. Measuring the change of attenuation gives more effective information to evaluate thermal shock damage than that of velocity nondestructively. The flexural strength was also measured for the thermal shocked specimen. The flexural strength was decreased rapidly at the point of time of observation of microcracks on the surface of specimen, and the flexural strength decline by the crack growth caused thermal shock cycles was slight.