Abstract: A new method for testing the center deviation of the rotating UT line is developed in order to get quick and timely mastering of the rotator center deviation data of the rotating UT line for the seamless steel pipe，and the accuracy change of the pipe roller conveyor so as to ensure the accuracy of the UT result. The mechanical structure of the ultrasonic rotator is analyzed，and its dimensions are confirmed to determine the incident angle of the longitudinal chiplet probe. And the accuracy of the rotator probe center，i.e.，the consistence of the probe acoustic beam center with the rotator center is determined via the consistence of positions of the chiplet different channel interface waves as displayed on the oscilloscope. Thanks to this new method，the consistence of the rotator with the probe center is ensured so as to meet the needs by the production and quality inspection.