Abstract: During the overhaul of a power plant, all tubes of two industrial cooling water heat exchangers were tested by eddy current testing, and many defects were found. The defects were analyzed by data and the types of the defect were determined. Furthermore, the position and type of defects were statistically analyzed. The conclusion is that the vibration and wear of the baffle bar is the main reason for the formation of defects. Combined with the structural characteristics of the container, it is suggested that the so called "phase-depth of the defect" method is a more reasonable quantitative method for this kind of wear defect.