Abstract: Eddy current displacement sensor is a type of microdrivers using the theory of eddy current to non-contact measuring the displacement precisely. G-radiant cooler has been used to cool the infrared detectors of the Medium Resolution Spectral Imager (MERSI) for the FY-3 Meteorological Satellite. The long and short wavelength HgCdTe infrared detectors are installed on cold stage and intermediate stage respectively. The optical paths of G-radiant cooler will produce irregular deformation because of the low temperature and the residual stress. The study has measured the deformation and the place of the optical paths at low temperature in order to achieve the cryogenic optical adjustment. Eddy current displacement sensor is a reasonable choice for measuring the deformation in the low temperature and vacuum condition.