Mental fatigue prediction using the electroencephalogram (EEG) has widely been studied. EEG definitely changes when one feels fatigue. However, the challenge is that the accurate results of fatigue prediction are from how to select the EEG interval of interest for real-time prediction. This paper proposes a novel method for efficiently selecting the EEG signal during fatigue period. Eye-blinking (EB) signs detected via the electrooculogram (EOG) are employed as the marker. The EEG band powers are further extracted as the features. The results illustrate that the proposed marker is possible to be efficiently used to predict the mental fatigue state in real-time.