Based on a lot of dynamic triaxial tests, some dynamic characteristics on intact loess under the train vibration load are studies. The results showed that when the intact loess was under certain dynamic stress, strain increased with the increase of the number of vibration, and decreased with the decrease of consolidation stress. The relation between stress and strain can be fitted with hyperbolic model under certain conditions. When dynamic stress was smaller, strain could be fitted linearly with dynamic stress. And the growth rate of strain increased with the increase of the number of vibration.