Abstract: Ultrasonic phased array testing technology is an advanced ultrasonic nondestructive testing technology. Ultrasonic phased array technology can achieve flexible, controllable synthesized ultrasound beam and freely control the focus point position by exciting each element of ultrasonic array transducer with independent phase delay. Based on the synthesis of phased array focusing approach experiment, a 16-element array signal acquisition and processing of experiment system was designed. Test experiments to the piece were carried out with this system. The experiment result fit with the actual defects. Result showed that this method could achieve the effect of phased array focusing, which greatly improved the detection signal noise ratio and sensitivity, also verified the ultrasonic phased array testing method was feasible. Through the experimental test of defect detection, especially with the contrast focusing and non-focusing detection experiment, the results showed that phased array technology could improve the defect detection capability.