Abstract: In order to study the static and dynamic performances of cut subgrade of high-speed railways in medium-strong expensive soil area, model tests with a large scale of 1∶1 are performed. A cyclic load with frequency of 4 Hz and excitation of 1000000 times is imposed on the subgrade model under three kinds of working conditions (dry, raining and groundwater level rise). The results show that the dynamic stress in the subgrade beneath the track is mainly affected by the working conditions and not significantly affected by the vibrating number. The dynamic stress attenuation curve is conic in the vertical direction. The dynamic deformation is affected by the working conditions and vibrating number, that is, with the increase of the vibrating number, the deformation increases under the dry and raining conditions at first and then tends to be stable, and the subgrade rises because of the swelling deformation of expensive soil when the groundwater level increases. The in-process deformation difference is induced during the asynchronous swelling or shrinkage deformation process of expansive soil and causes the rail surface elevation to change repeatedly, and the maintenance work for track lines is greatly increased.