Abstract: SnO₂/MWCNTs composite modified anode was prepared by electrodeposition and impregnation methods, and was applied to modify the anodes of the marine sediment microbial fuel cells (MSMFCs). Electrochemical performances of the MSMFCs with the SnO₂/MWCNTs composite modified anode were investigated.Resultsindicated that the electrochemical activity, kinetic activity of electron transfer and the capacitance property of the SnO₂/MWCNTs composite modified anode were 28. 26, 983. 7 and 43. 14 times as high as those of the blank; anodic charge transfer resistance was about 1/4 of that of blank group.The maximum power density of the modified MSMFCs was 1 085. 1 m W/m², 2. 17 times of that of blank group. Mechanism analysis of the composite modified anode showed that the MWCNTs could raise the conductivity of anode, and SnO₂ made the redox reaction more easily, resulting in increased capacitance performance of the anode; it was the marine weak alkaline condition that enhanced the synergistic effect of SnO₂/MWCNTs composite so that the modified cell showed excellent performance.