The paper uses finite element software ANSYS to establish the train-ground-piles coupled dynamic model.By means of the transient dynamic method,it analyzes isolation effect on four kinds of structure parameters including the pile depth,the pile diameter the section form and the material.The vibration isolation mechanism and the rule of piles are studied.The analysis indicates that the change of pile depth,the pile diameter and the material have sharp influence on the vibration isolation effect,but change of the pile section form has little influence on the vibration isolation effect,because the effectiveness of piles depends on its diffraction effect to waves.