表面开口类缺陷的检测和高度的测量对核电设备寿命的评估意义重大。分别利用常规超声端点衍射法与TOFD（衍射时差法）方法对表面开口缺陷的高度进行了测量并对结果进行了比较，得出结论：检测高度小于4 mm的开口缺陷时，常规超声端点衍射法分辨力下降严重；TOFD方法利用A扫信号可以区分1 mm高度的开口缺陷；随着表面开口缺陷高度的增加，两种方法测量结果基本一致。

It is of significance to detect and measure the height of cracks in order to assess the life of nuclear power equipment. In this paper, the measurements of the height of surface breaking defects by conventional UT tip diffraction method and TOFD method were compared. The conclusion was drawn:for breaking defect of height being less than 4mm, the resolution of conventional UT tip diffraction method decreases sharply; using TOFD with A scan can distinguish breaking defect of height greater than 1mm. With the increase of breaking defect height, two methods of measuring results are basically identical.