Abstract: Based on the field test,the dynamic responses (dynamic stress and strain) of a roadbed-bridge transition section under the disperse impetus locomotive with high speed are studied in this paper.It is shown that the variation of the maximum and average dynamic response curves is same. On the same speed condition, the dynamic response curves and the dynamic response increment curves are in the shape of "V" and "N" respectively in the direction of railway line;and in the direction of depth the dynamic response curves decline with the increase of depth and the declining extents are bigger within shallow roadbed (about 0.6 m), with the speed increases the dynamic responses in the direction of railway line and depth decline,and the declining extents are related to the train speed tightly. At one time, the variation coefficient formula of train axes-weight is put forward to forecast general trend of variation of the dynamic responses in the transition section roadbed, and a design idea is advanced that"excess height"of roadbed can reduce the differential settlement and the dynamic response of transition section roadbed. The test study provides an important basis for the design and construction of the transition section roadbed of express railway.