Abstract: According to the principle of phased array ultrasonic testing and combining with the characteristics of weld of small tube, small tubes with weld defects of φ34 mm×4 mm specifications (outer diameter×wall thickness) were chosen for phased array inspection and comparisons with other test results were carried out. Through the analysis of field test data, phased array ultrasonic testing technology can visually, quickly and accurately detect defects and ensure the safe operation of equipment.