Background: In order to satisfy the researchers’ strong requirement for a three-dimensional fine structure of the sample with high spatial resolution

the Nano-CT system based on the BL08U soft X-ray microspectroscopy station of Shanghai Synchrotron Radiation Facility（SSRF） has been developed

but sample drifted seriously while CT scanning.Purpose: The sample drift greatly reduces the accuracy and efficiency of CT experiment

so that an accurate online automatic calibration is necessary.Methods: Sample drift trajectory can be recorded in the rotation process by visible light microscope（VLM）

and then the shift data of every angle can be obtained which can be used in calibration online.Results: The sample drift had been calibrated and limited below 1 m after the calibration algorithm

which meet the accuracy requirement of the CT experiments.Conclusions: Automatic calibration greatly improves the efficiency and accuracy of Nano-CT experiment.