介绍了小直径棒料内部质量检测的超声双晶探头法和水浸聚焦检测方法。采用现有的对比试块和10 MHz水浸聚焦探头，完成了 6和8 mm棒材中 0.5 mm当量的原材料检测质量要求，解决了双晶探头损坏后该类棒材检测能力的不足，且检测效果理想，检测过程易于控制，非常适宜于小批量、多规格小直径棒材的检测。

Ultrasonic testing methods of small diameter bars with double crystal probe and immersion focusing probe were introduced. With 10 MHz immersion focusing probe and reference block, high sensitive ultrasonic testing with 0.5 mm equivalent for small bars about diameters 6mm and 8mm were realized, which solved the problem of testing bars after double crystal probe being damaged. The testing result showed that immersion ultrasonic method was very suitable for testing small mount and multi-specification bars and easy to control testing process.