Abstract: According to the different relationships between machine and human limb,the mechanisms in the rehabilitation devices are grouped into different categories,and a concept of bio-syncretic rehabilitation mechanism and its characters are presented.On the basis of the analysis on the mechanisms of ankle and some existing robots for its rehabilitation,a novel parallel mechanism with elastic elements for ankle rehabilitation is presented as an example of the application of the new concept.The mechanism not only meets the requirements of ankle rehabilitation motions such as eversion/inversion,dorsiflexion/plantarflexion,adduction/abduction,but also can supply traction to the ankle.The output degree of freedom,configuration degree of freedom and the rationality of selecting actuated joints of the mechanism are discussed.The inputs of the mechanical drives and biological drives during the motion of ankle rehabilitation are calculated,and the orientation of ankle is calculated when the two groups of drives are given.Taking the dorsiflexion/plantarflexion motion of the ankle rehabilitation as an example,the force on each mechanical limb is given,and the relationships between the input of each mechanical drive and the orientation of ankle are given.