Using a special Test-Bed, the temperature and the grain moisture content variation in different locations was measured continuously, under the condition of maintaining a large temperature difference between two terminals of grain layer. The results show that the temperature gradient can enhance corn-drying process, and there are two modes of the promotion: 1. The temperature difference direct drive the moisture migration; 2. The temperature difference can generate air convection, and accordingly promote the drying rate. However, the speed of moisture migration originated from air convection was much higher than driven by temperature gradient.