Abstract: The gaps between steam generator tubes and anti-vibration bars will affect the tube vibration wear. In this study, taking CPR1000 unit type 55/19B steam generator tube and anti-vibration bar as experiment model, rotating probe was used to establish the relationship between eddy current signal and tube-to-AVB gap. The results showed that the monotonic decrement of eddy current voltage amplitude with the increase of the gap could be represented by the EXCEL polynomial curve and the optimization of the curve was needed before its usage.