Flexible hinges are widely used in micro robotic. Its rigidity directly influences an organization's terminal localization. Its actual structure geometry size cannot satisfy the theoretical analysis completely in a theoretical supposition condition. In this paper, we analyzed the rotation rigidity of half arc flexible hinges in different parameters using finite element software ANSYS. The errors are discovered and compared with theoretical result. An analysis of changes of parameters on the performance of arc flexible hinge was carried out, though the graph of the flexible hinge's parameters and its performance. The key manufacture parameters that affect the performance of arc flexible hinge the most and rules of design are given, which can provide directions of design precision for the flexible hinge.