This paper described the relationship between EEG signals and MI in BCI system. EEG signals
are used to classify the direction of motioninto two kinds: left and right. We extracted features
from original EEG data using STFT and put them into CNN. The result showed that the
framework of STFT-CNN had higher average test accuracy. Furthermore, the generations of
motor imagery were analyzed, and the result showed that better classification results will appear
in the middle stage with its classification accuracy reaching 92.8%