A kind of auxiliary device for ankle rehabilitation based on rigid-flexible combination drive is introduced. The device has two degrees of freedom,while three-dimensional movement of the ankle can be achieved approximately. To analyze the rehabilitation effect of the device,the working spaces are studied. First,the device working conditions are given,and the constraints of the working space are analyzed. Then,the digital solution model for working space is established. Finally,the working spaces of the device are calculated by using Matlab. The analysis results can be used to optimize the device structure and determine its characteristic parameter. The process of this research can be as a reference for research of working spaces of mechanism with multiple movement mode.