Abstract: For heaters in nuclear power units, U-shaped heat transfer tubes of different types of heaters were tested with different eddy current testing methods. Comparisons were conducted on conventional eddy current testing and far field eddy current testing through following aspects, such as testing principles, scheme implementations and defect analyses. Results show that, conventional eddy current testing has a high sensitivity for detecting depressions, while far field eddy current testing has a high sensitivity for detecting internal and external injuries with a certain depth. Defects in high and low pressure heaters are mainly concentrated in the outer U-shaped heat transfer tubes and the transition zone between the straight tube and the bent tube. This may provide a reference for eddy current testing of heat transfer tubes of high and low pressure heaters in similar nuclear power units.