Abstract: Based on the dispersion and displacement characteristics of longitudinal axially symmetric mode guided waves in copper alloy tubes, the L(0,2) mode at 0.49 MHz was employed. Tests of copper alloy tubes with various defects were carried out. It was showed that the L(0,2) mode had good ability to detect various defects in copper alloy tubes. The echo amplitude from defects depended mainly on the radial and circumferential dimentions, and the longitudinal length of defects had little effect on the amplitude.