Degradation of the elderly's mobility is a long process. How to provide a device to help them have a better life quality is very important. This composite assistive device design that combines the functions of a rollator and a wheelchair which is designed to accompany the elders in the process of gradually losing their vitality. Users can find corresponding solutions depending on their physical conditions. At the same time, increasing the elderly's willingness to go out. It can greatly improve their health, social and emotional connection with their family.