Abstract: According to GB 4234.1-2017, there should be no δ ferrite phase, χ phase and σ phase in stainless steel micro structure, but no relevant detection method was provided. The harmful precipitated phases in UNS S32750 stainless steel were identified by using the method of combining backscatter image technique with scanning electron microscope and X-ray energy spectrometer. The results show that the method could meet the technical requirements of GB 4234.1-2017, and could be used as an important means to control the quality of stainless steel for surgical implantation.