Abstract: Generally， the optimum design of a sector gate is simplified as a planar system， or only to optimize various components. The former ignores the link between each component for the sector gate as a space system， while the latter， the optimization of various components, cannot be equivalent to the optimization of the whole gate structure. In this paper， according to the real three-dimensional situation of a sector gate， we use ANSYS Parametric Design Language（APDL）to re-develop the finite element model for the sector gate. This method can combine the accuracy of FEM structural analysis with the high efficiency in solving extreme value problems， so it resolves the sector gate′s three-dimension optimization problem successfully.