Abstract: In the process of manufacture, installation and operation of steam generator, the relative position of the anti-vibration bar and the U-shaped heat exchange tubes may be changed due to secondary side effect such as water or outside force, thus possibly resulting to its failure. Using eddy current testing method, the information on the relative location of anti-vibration bar of U-tube can be obtained. The position detection of anti-vibration bar after the hydraulic test can be used as a benchmark during the steam generator operation, which may play an important role for the safe and effective operation of the evaporator. The application of this type of eddy current testing has solved the problem of how to measure the relative position of heat exchange tube and anti-vibration bar for the existing steam generators.