Abstract: In seamless steel tube flaw inspection, the URP automatic ultrasonic testing machine is capable of simultaneously high-speed detecting both longitudinal and transversal flaws, measuring wall thickness, and detecting defective lamination, featuring such advantages as high sensibility and stability. Elaborated in the essay are he main aspects of the said URP detection system, including operation principle, equipment configuration characteristics, operation and maintenance criteria, and the on-line operation incorporated with the seamless steel tube-making plant. Relevant operation practice shows that the detection system is able to fully meet the requirements for ultrasonic detection of seamless steel tubes at metallurgical mills.