Abstarct: The aim of Robotic rehabilitation is delivering the weak patient to the desirable level of physical ability. In this thesis, a three degrees of freedom parallel robot with unique direct kinematic solution is selected. Moreover by an optimization procedure, the optimum dimension design is proposed in order to use for the ankle rehabilitation. Since each of the legs of the robot consists of a pneumatic cylinder, studying and controlling of the pneumatic actuators are discussed. Pneumatic actuators controlled by servo valves in a way that the input and output discharge to cylinder is specified. In this regard, the observer is designed to estimate the pressure in the cylinder chamber. Also, a robot leg is designed and the robot dynamics is analyzed baxsed on the whole manipulator mechanism. Upon completion of the design phase, the main components of the parallel robot including the control circuit and the designed robot leg are fabricated. combined experimentally and tested. Finally its experimental and theoretical results are presented and verified.