Abstract: Some technical difficulties encountered in ultrasonic testing site of smalldiameter tube were introduced. Some problems, such as the refraction angle of the probe, the test block, the test compensation amount, the defect judgement and others, were researched and analyzed. Some matters needing attention in ultrasonic flaw detection of smalldiameter tube were pointed out.

Key words: small-diameter tube, ultrasonic testing, refraction angle, test block, compensation amount