In this study, we demonstrated a Wearable Mobile Electroencephalogram (EEG)-based Brain Computer Interface System (WMEBCIS) with foam-based dry electrodes embedded. According to the previous studies, many kinds of BCI systems have been proposed and target the applications on sensors and information techniques. For daily life EEG monitoring by using the BCI systems, the sensors have employ a key technique for ensuring the data quality. In view of this, a novel dry foam electrode was designed and applied for the wearable EEG acquisition device in our WMEBCIS. The developed dry electrodes can achieve the quick-placement and high signals quality under no skin preparation and without gels applied. Most importantly, due to its softness advantage, the developed electrodes can fit properly on the skin surface to maintain low skin-electrode impedance and reduce motion artifacts under movement. By using the specific mechanism of our wearable EEG acquisition device, it can be worn conveniently and can maintain the electrode-scalp contact area to acquire good EEG signal quality effectively. Therefore, the wearable EEG acquisition device is suitable for long-term EEG monitoring in daily life. In words, our WMEBCIS was also demonstrated for a cognitive application on drowsiness detection.