The existing semi-dry electrodes release electrolyte by a pressure-driven mechanism, and it is liable to cause unstable recording signals due to uncontrolled release of the electrolyte. To resolve this problem, two types of semi-dry EEG electrodes have been developed by using macroporous hydrogels and porous ceramics as electrolyte permeable materials. The electrolyte permeable material and electrolyte concentration of the semi-dry EEG electrodes were optimized firstly. Then the release rate of the electrolyte, electrode-skin impedance, electrode potential, and EEG signal quality of the optimized semi-dry electrode were systematically evaluated. When porous ceramics were used as the electrolyte permeable material and 3.5% NaCl worked as electrolytes, the semi-dry electrode-skin impedance at 10 Hz was low and stable. The optimized ceramic semi-dry electrode had a relatively low electrode-skin impedance (42.1 ~ 51.4 kΩ) and a small potential drifting (2.9 ± 1.4)μV/min, indicating excellent electrochemical performance. Moreover, the ceramic semi-dry electrodes could effectively record the visual evoked potential (SSVEP), and the signal quality was highly similar to that of “gold standard” wet electrodes.