Abstract: Introduced here in the assay is an ultrasonic guided-wave NDT method for inspection of small- sized seamless steel tubes. Put forward are the specific detection process, and the method for evaluation of the detection result. Lots of cases of site operation practice shows that the said NDT process is very sensitive to common defects of the seamless steel tube like crack, outer fold and fin, etc., and the inspection effectiveness is ensured. Nevertheless, there are some disadvantages staying with this process, such as low detection rate of pitted defects, and that in case of identifying inner defect of small-sized heavy tubes (D≤76 mm, S>10 mm), it will be rather difficulty to perform the detection due to the low signal-noise ratio.