Stroke patients have some motor deficits, but they can regain their motor abilities by rehabilitation. In the aspect of rehabilitation, voluntary movement is very important. We propose a system which can make a closed loop in brain for stroke patients like voluntary movement. Event Related Desynchronization (ERD) is used to extract patients' motor intention, and then Functional Electrical Stimulation (FES) stimuls their paralyzed muscles. In many Brain Computer Interface (BCI) researches, subjects are trained for several months or years to do the task, because of the difficulty to extract clear ERD without training. Thinking about applying for stroke patients, motor imagery training should be shorter, because of the brain plasticity. We did a pilot study about the effect of visual feedback training for three days with healthy subjects. The result indicated that ERD could be clearly extracted in three days, but the training effect differs in each subjects.