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BackgroundSextupoles are an important component of storage ring octonal unit in high energy synchrotron radiation sources. They require complex technological processes and precise center extraction. Therefore, it is necessary to find out the most reasonable calibration scheme for the mechanical center.PurposeThis study aims at the calibration scheme for the mechanical center extraction of high energy photon Ssurce (HEPS) sextupoles, and obtaining the corrected mechanical central coordinate system.MethodsThe method of directly measuring the reference plane of the sextupole was adopted for the mechanical center calibration of magnets. By rotating the conventional calibration coordinate system with a given pole seam deviation angle, the three polar seam surfaces were brought closer to the theoretical positions to decrease the main diagonal component of the sextupoles. The mechanical center calibrations were performed twice for each hexacode iron to further reduce the impact of the polar seam error.ResultsThe calibration results show that the calibration repeat accuracy is 0.005 mm for the sextupole. The standard deviation between the measured value and the design value of the pole seam spacing is 0.015 mm. Additionally, the standard deviation of the reference point before and after the rotation of the coordinate system is 0.09 mm, with a maximum rotation angle of 0.6 mrad.ConclusionsThe calibration scheme of this study can be used to improve the calibration accuracy and provide reference for the calibration of similar equipment. It ensures smooth installation of accelerator devices and is of significant importance for accelerator collimation measurements.