Abstract: Nowadays TMCP technology is widely used in steel industry. After the TMCP steel processing technology, the mechanical properties of steel can be improved, such as material strength, toughness and weld ability, but at the same time this process will result in minor changes in the acoustic performance and the impact on the speed of sound may cause the probe beam angle changes. In the ultrasonic testing of welded joints, the angle of refraction and the material velocity probe change shall result in some errors in the defect location. In order to reduce these errors, some amendments are needed to achieve accurate positioning of the defect quantification.