对小径管检测前校准仪器时的一个特殊回波产生原因进行了研究，结果表明，该特殊回波经过多次反射后被探头接收，传播路径复杂。因此在超声波检测时，不仅要靠经验对回波进行判断，还需要对可疑回波进行细致的演算和推敲，避免因误判造成不必要的损失，另一方面也可提升检测人员的技术水平。

The cause of a special echo generated on adusting the equipment for the test of small-diameter tubes was analysed in the paper. The results showed that, the special echo was received by transducer after the ultrasonic wave was reflected for several times, and the propagation path of echo was very comlex when carrying out ultrasonic test. Technicians should not only interpreter the echoes according to experience, but should also calculate and analyse any suspicious echoes to avoid any misdetection. Meanwhile, the technological level of technicians can be improved greatly in the process of calculating and analysing.