In order to improve the performance of the lower extremity exoskeleton robot,structural optimization for parts of the lower extremity exoskeleton robot is required.The modal data of the part were used as the optimization basis for the thigh board by using the topology optimization method.Firstly,the 3D model of the part was built and imported into the Workbench software for static analysis and modal analysis.The maximum stress and maximum strain of the thigh plate at the maximum working load and the natural frequency and maximum amplitude of the first 4 orders of the thigh plate were obtained.Then,the grooving process was performed,and the groove width was set as a variable to solve the modal parameters under different groove widths.Finally,according to the natural frequency and amplitude parameters,the optimal value of the groove width was selected in the case of meeting the weight reduction requirement and the part strength requirement.After the slotting treatment,the weight of the thigh plate is obviously reduced,the natural frequency is decreased,the antivibration performance is reduced,but the working condition can still be met,and the static analysis of the part can also meet the requirements,so the topology optimization is verified.It has certain reference value for structural optimization of lower extremity exoskeleton robot.