针对TOFD检测应用最为广泛的平板对接焊缝，在常规TOFD检测中焊缝缺陷深度计算的基础上，进行了进一步的数学推导，得到了一种更简洁的基于时差的数学表达式，以用于缺陷深度的测量计算。该方法无需进行声速和探头入射点间距值的测量，只需利用TOFD检测设备读取有关的时间参数及人工输入板厚值就可进行计算，避免了声速、探头入射点间距值的输入精度导致的测量误差。并通过扫查TOFD对比试块，测量其中的横孔缺陷的深度，验证了该方法的计算精度和可行性，取得了满意的效果。最后,对于存在余高的平板对接焊缝，提出了为提高计算精度而进行板厚值修正的方法。

In view of the most wide application of TOFD in the field of plate butt welds, the article proposed a new and succinct mathematical expression of time differences to calculate the defect depth by further mathematical deduction on the basic of the conventional defect depth calculation in TOFD. The method can calculate the defect depth just only according to the time parameters read from the TOFD equipment directly and the manually input thickness of the plate. The method avoids the measurement errors of the defect depth resulted from the precision of the velocity and the value of probe center separation . Experimental verification was carried out by measuring the depths of the holes in TOFD block, the precision and feasibility of the proposed method was validated. The Experiment achieves a satisfactory result. In the end, the article discussed how to implement the thickness correction for the plate butt welds with weld reinforcement.