Abstract: After a description of the objectives and significance of upper limb rehabilitation robots, a comprehensive review of research achievements about upper limb rehabilitation robots at home and abroad is presented. Based on the review, state of the art of two types of rehabilitation robots is discussed mainly from mechanical design point of view, i.e. end-traction rehabilitation robot and wearable exoskeleton rehabilitation robot. Some typical upper limb rehabilitation robots' structure characteristics are analyzed. Finally, the main problems associated with existing upper limb rehabilitation robots are discussed from mechanical design perspective, focusing on the exoskeleton rehabilitation robots.