In order to study the problem of riding quality of an exported diesel multiple unit that uses a powerpack as its power source and solve the problem of excessive local vibration in the installation position area of the power pack and the body, the ride index of the diesel multiple unit was obtained with experimental and simulation methods. In addition, the influence rules of the local vibration affected by high local stiffness of the body in the powerpack′s installation position and the reasonable isolator stiffness of the body floor were analyzed. Results show that: the ride index of the diesel multiple unit was good, and there was no coupled vibration between the powerpack and the body; high local body stiffness was beneficial in decreasing the lateral vibration, however, the vertical vibration will slightly increase; laying isolator in the floor of the body can significantly reduce the local lateral and vertical vibration, research results will provide reference for practical engineering applications.