The work aims to design a sit-stand dual-purpose mobility assistance robot tailored for mildly disabled or weak elderly individuals based on the TRIZ theory. In the problem identification phase, an analysis on the system components of the sit-stand dual-purpose mobility assistance robot was conducted. Subsequently, a functional model diagram was established based on the interactions among these components. The root causes of the problems were determined by causal chain analysis, followed by preliminary analysis according to the trimming method. Su-field analysis, technical contradiction analysis, and physical contradiction analysis were employed to obtain ideal solutions to the problems and formulate design concepts. The application of TRIZ theory tools led to the ideal solutions, resolving issues with components like the backrest, protective gear, armrests, and control panel. Therefore, the innovative design and optimization of the sit-stand dual-purpose mobility assistance robot were carried out. In conclusion, based on the TRIZ theory, a sit-stand dual purpose mobility assistance robot is designed to enhance the elderly's outdoors experience. Additionally, it provides valuable insights for the design of similar dual-purpose products.