Abstract: Flow induced vibration of a four-span tube bundle with large gap anti-vibration bars (AVB) supports was experimentally studied. The tube bundle was arranged in rotated triangular pattern. Three AVB supports divided the straight tube bundle into four spans. Only part of one of the middle span tubes was subjected to cross flow. The response characteristics of the displacement and frequency of the heat transfer tube with the pitch velocity in the test increased from 3.3 m/s to 14.7 m/s were obtained. The results show that the vibration frequency increases with the pitch velocity in streamwise direction and transverse direction in proper order. The vibration mode of the tube changes from the state of one effective AVB support and two ineffective AVB supports to the state of three effective AVB supports. The fluidelastic instability (FEI) critical velocity for the tube tested is 14.5 m/s. Five empirical correlations were used to predict the FEI critical velocity, and the predicted results were compared with the experimental results. It is found that the Chen correlation is best. The predicted FEI critical velocity by Chen correlation is conservative, and the relative deviation from the experimental value is 21.4%.