在检测小径薄壁管焊缝时需要使用聚焦探头。为了测试所用聚焦探头的相关技术指标， 如聚焦性能、探头声束准直性、探头分辨力、探头K值以及前沿等，设计了一种特殊试块。介绍了试块的设计图纸以及其上人工缺陷的形式，同时介绍了采用该试块测量不同技术参数的方法以及评价方式。

Focusing probe was used during the ultrasonic testing for the girth weld on the thin-wall and small-diameter tube. In order to get the technical parameters of the focusing probe, such as focusing characteristic, acoustic beam, resolution, K-value, and front and so on, a special block was designed. The design drawing and the artificial defect on the block were introduced, and the testing method on the different parameters and evaluating method was introduced also.