Dynamic response field tests of a subgrade-bridge transition zone in the Menghua heavy haul railway were carried out to investigate the distribution of dynamic stress, dynamic displacement and vibration acceleration in the transition zone.Subsequently, a 3D FEM model considering the coupling vibration of roller-subgrade was established to study the equivalent stiffness distribution along the transition zone and the contact force response between the roller and subgrade surface.The results show that with the depth of subgrade increases, the diffusion angle of dynamic stress gradually decreases, the diffusion angle of the subgrade depth between 0.2-3.0 m is 78.2°-55.0°, and the diffusion angle of the inverted trapezoidal transition is larger than that of the general subgrade.Compared with the train load, the vertical dynamic stress caused by the excitation of the roller is attenuated faster in the subgrade and the attenuation is the largest in the surface layer.The dynamic lateral pressure coefficient in the surface layer is 0.35-0.53 in the direction of the roller leaving the abutment, and the direction toward the abutment is 0.24-0.36.The dynamic lateral pressure coefficient of the inverted trapezoidal transition is smaller than that of the general subgrade.The equivalent stiffness of the transition section is between 74.8-87.2 kN/mm, which decreases linearly with the distance from the abutment.During the vibration wheel excitation process, the peak of the maximum contact force of the roller-subgrade surface in the transition section is larger than that of the general subgrade section, and the maximum contact force peak of the transition section increases with the stiffness difference of the transition zone.