During rice processing and storing, one of the important factors to reduce rice quality is wet stress in rice kernel. In this paper, the wet stress cracks in rice kernels were studied under the normal temperature. The dynamic image analysis method was used to measure and obtain linear expansion coefficient of rice. The methods to estimate the moisture diffusivity and the absorption depth were developed for the fissure rice caused by the wet stress. A preliminary research was conduct to determine the range of moisture gradient inside rice kernels when wet stress cracks emerged, which located from 6.0 to 7.5%/mm.