Abstract: The helical tube bundle is widely used in fast reactor and fourth generation nuclear power reactor because of its compact structure and high heat transfer efficiency. The bundle arrangement of adjacent layers wound in the opposite direction for helical-tube heat exchanger is constantly changing in the axial section of the helix. In addition, turbulence makes the fluid in the shell-side present flow instability in the subcritical region, and the vibration form of coil tube bundle coupled to the fluid is not specified. There is no basis for the safety prediction and evaluation of FIV (flow induced vibration) for the bundle wound in the opposite direction. The robustness of the 3D fluid-structure interaction numerical model was verified by measuring the in-plane and out-of-plane vibration responses of coil tubes. In order to prove the reliability of 3D fluid-structure interaction numerical models, an impact test system about FIV was designed and established. On the basis of the impact experiment to verify the excitation model in regard to helical tube bundle, the mechanism of the relative position of the tubes and the structural parameters of the tube bundle on the vibration response of the helical tube was systematically studied by using the helical tube bundle excitation model. The influence of pitch diameter ratio between adjacent tubes on the vibration response of the tubes is stronger than that of pitch diameter ratio between tubes in the same layer and helix angle. The more compact the bundle arrangement is, the greater the vibration response of the tubes is, and the more drastic the amplitude fluctuation is. With the increase of helix angle, the difference of vibration response between front tube and back tube became smaller, and the amplitude increased slightly. With the increase of flow rate between the tubes, the amplitude in both directions increased gradually, while the amplitude in the out-of-plane is significantly larger than that in the in-plane, and it is the first to occur fluid-elastic instability. Based on the quasi-static model, the semi-empirical formula of critical velocity for the tube bundle is presented. The paper addresses the FIV mechanism for helical tube bundle with adjacent layers wound in reverse, and lays a theoretical foundation for the structural design of the helical tube bundle and the calculation assessment of FIV of the heat exchanger, which is great significance for the design and application of helical tube heat exchanger.