Abstract: The torsion equivalent stiffness describing the rotation capacity of the LET flexure hinge is analyzed. The conception of extension and compression equivalent stiffness is proposed to ensure the rotation accuracy of the flexure hinge, and the deduction process of equation for calculating this equivalent stiffness is presented. An optimization model is established to enhance the rotation capacity and accuracy of the flexure hinge with structure parameters as design variables. In order to realize parameter optimization, the Simulated Annealing (SA) is applied to the optimal design model. A better rotation capacity and accuracy of the flexure hinge is achieved after optimization．