Abstract: Elaborated by the coauthors in the paper are the principle of detection of the steel tube lamination defect. Based on the identified characteristics of occurrence of the lamination defect and its distribution spots in the steel tube, the reference pipe with standard reflector is prepared for dynamic calibration of the automatic ultrasonic detection system. Also detailed are the procedure for setting the lamination-detecting gate, and how to properly determine relevant parameters such as probe rotation speed, the pulse repetition frequency of the instrument, and screw pitch, etc. to consistently identify the standard reflector under the dynamic condition so as to perform the automatic detection of lamination defect of the pipe body. The effectiveness of the above mentioned method is verified through relevant on-the-site detection operation activities.