Abstract: Described in the paper is the application of the HF constant potential technique with operation frequency over 80 kHz to the X-ray detection process for helical weld pipes.With the said technique,the highpower field effect tube(IGBT) is used to produce HF pulse voltage via the AC-DC-AC reverse transformation mode,and the pulse width is adjusted under fixed frequency via the feedback signal from the closed-loop circuit so as to bring about control of the hi-tension circuit and primary circuit of the high-voltage transformer.Thanks to such a technique,certain chronic problems as staying with the power frequency X-ray detection operation.