Abstract: The method of measuring direction of mechanical deformation by detachable-double- reference-beam double- exposure holography is proposed. In the optical system designed, a spread beam is divided in the two reference beams and one object beam with the help of the two planar mirrors．Thus the double-exposure interferogram of the measured object under constant deformation can be recorded．This kind of interfero-gram carries double informations on quantity and direction of deformation of measured object．Problem on information of deformation direction is analyzed in theory. The method of using detachable-double-reference-beam double-exposure ho-lography to measure deformation direction is described. Ex-perimental results are given.

Key words: Detachable double-reference-beam, Direction of mechanical distortion, double-exposure-holography, Measure