Abstract: Abstract To measure the gap distance between the heat transfer tube and the antivibration bar in the steam generator, eddy current testing was used for measurement research to obtain the relationship between the distance between the heat transfer tube and the antivibration bar gap and the signal amplitude, as well as the recommended range of rows for measuring the antivibration bar gap on the heat transfer tube (with antivibration bars on one side of the heat transfer tube) when using a Bobbin probe. The obtained relationship curve and the recommended range of rows were compared with actual data to demonstrate their practicality in on-site work.