Abstract: The weir of the spillway chamber is an important part of the sluice chamber, of which the thickness has a great influence on the safety of structures in spillway sluice chamber design as well as on the project investment. The optimization of the weir structures almost relies on the determination of the sizes of the main components,and there is rare optimization of the thickness of the sluice chamber weir while the main component size of the chamber is confirmed. Considering six kinds of weir body shapes, we establish a finite element model of different solutions by the software ANSYS, and then do the analysis of the stress of the structure in this study. The optimization takes the excavated volume as the design variables, and takes the stress of bracket, clevis and pier as the single objective to establish an optimization model. Then we consider the stress intensity, and apply the Lexicographic method to optimization design of the weir thickness and then get the optimal size of the sluice chamber weir. The study provides a basis for the design of the spillway of the sluice chamber structure. The research method and design idea can provide a reasonable reference for other similar spillway sluice chamber weirs.