The invention relates to a lower limb rehabilitation robot system based on myoelectric signal feedback, and a control method thereof. The robot system comprises a mechanical part and an electrical part. The major application targets of the method are rehabilitation patients at early and middle stages. When a patient uses the method to perform rehabilitation training, myoelectric signals of moving muscles of the patient are acquired in real time, the motion intention and the motion speed of the patient are identified, the expected tracks of robots are generated, the expected tracks of driving parts are obtained through inverse solution of kinematics, and motors are driven to output through a designed fuzzy PID (Proportion-Integration-Differentiation) controller. After each motion period, the acquired myoelectric signals are analyzed to judge whether the patient is in a fatigued state or not. When the fatigued state is larger than or equal to a set fatigue threshold, the original output is corrected to remind the patient. After the fatigue is relieved, the rehabilitation training can be resumed. The lower limb rehabilitation robot system based on the myoelectric signal feedback, and the control method thereof have the advantages that since the intention and the muscle state of the patient are identified by using the myoelectric signals, and the myoelectric signals are introduced into control, the participation awareness and the training safety of the patient can be well improved, and the rehabilitation effect is effectively improved.