Abstract: In order to enhance the flexibility of wearable lower limb exoskeleton robots, a lightweight design scheme based on topology optimization is explored. Based on the topology optimization technology, a lightweight design is carried out for the thigh guard of a lower limb exoskeleton robot. The material distribution of the thigh guard under actual usage conditions is analyzed, and the corresponding lightweight scheme is determined. The results show that, while meeting the requirements of actual operating conditions, the lightweight scheme reduces the weight by 15.1%, providing an effective approach for lightweight research of the similar components in lower limb exoskeleton robots.