The Walking Assistant Robots(WARs) developed by our institute are introduced in this paper. First, three prototypes with different mechanical and control structures are introduced and compared. Then as for the prototypes Ⅲ, its main framework and three important function modules including force sensor based human-machine interaction, Omni-directional vision based tracking and guiding system, and web-based monitoring system are described in detail. The WAR can recognize the user’s intents and execute different assistant functions, such as seating or standing-up assistant, walking assistant, human tracking, location, obstacle detection and avoidance. The application in an elderly care center shows WAR has a perfect and stable performance.