Abstract: With aniline(ANI) as the precursor, the composite modified cathode PANI/ACFC and PANI/ACF were respectively prepared to investigate their electrochemical performances. The results show that the exchange current densities of the PANI/ACFC and PANI/ACF cathodes are 1.905×10^-5A/m² and 7.122×10^-4 A/m², 4.2 and 157 times of that of the blank cathode, respectively. The maximum power density of MSMFCs reaches 150.54 mW/m²(PANI/ACFC), and 205.92 mW/m²(PANI/ACF) respectively, 3.2 and 4.3 times of that of the blank sample. It is speculated that the improvement of MSMFCs performance could be attributed to the PANI as an electron transfer intermediary, and a new electron consumption pathway on the cathode surface is proposed. The research result would be applied in the cathode designing of MSMFCs in deep sea.