Abstract: Aiming at the difficulty of conventional ultrasonic testing for HDPE hot-melt weld, phased array ultrasound (PAUT) and diffraction time difference (TOFD) were used to test the hot-melt weld. Through the detection and comparison of three pipe fittings with preset deficiencies, both methods can detect and locate the preset deficiencies accurately. The two methods can record and store the detection data, at least form A/B view, display intuitively, and facilitate the quantitative and qualitative evaluation of defects. It provides a new technical choice for nondestructive testing of hot-melt welds.