The work aims to conduct lightweight design of health care assistive devices and explore a comprehensive design method of product form lightweight and structure lightweight to reduce and alleviate the physical and psychological burdens of users. With protective boots as an example, firstly, the lightweight imagery was taken as the form design target, and the semantic difference method and principal component analysis were used to obtain the lightweight imagery and its typical representative samples; secondly, the visual dynamic form analysis was used to establish the mapping relationship of the lightweight imagery of the product form, and the initial form scheme was designed by the curve control method based on this relationship; then SolidWorks software was used to optimize the topology, determine the redundant part of material and provide guidance for structure weight reduction; finally, the mapping relationship was combined again to optimize the initial form design and obtain the final design scheme. The protective boot design scheme is evaluated. The simulation results show that the weight of the scheme is reduced by nearly 40%. The evaluation results show that the lightweight imagery is well evaluated, which shows the feasibility of the method and provides a new idea and method for the lightweight design of health care assistive devices.