The most of patients who have suffered a stroke experience upper limb impairments, making stroke the leading cause of adult disability. Robot-assisted task-specific training, which is an effective method to improve the performance of action, focuses on learning or relearning a motor skill. Circle-drawing with a robot together are not only beneficial as an adjunct to task-specific training and strengthening upper limb muscles, but also a part of the clinical evaluation protocols. In order to let the robot provide individuals effective prescriptions of rehabilitation settings to achieve precision rehabilitation for post-stroke patients, the acquirement and analysis of characteristics of upper limb muscles during the robot-assisted circle drawing rehabilitation training are most important. The surface EMG is presented and applied to characterize the development of upper limb muscles during motor rehabilitation. The experiment is carried out under the condition of normal people is guided by rehabilitation robot drive upper limb drawing accurate circle in passive mode. It found that the muscle tension of different upper limb muscles changed regularly during circle drawing with the rehabilitation robot guidance, which provides important theoretical basis for making more effective training plans and steers upper limb motor function for stroke rehabilitation.