One of the most promising applications of MFC is to use them treating organic wastes while accomplishing power generation. In this study, the effects of different electrode sizes on electricity generation performance and COD removal were investigated in dual chambered MFC. It was found that the maximum power density of S-MFC (the electrode anode size is 74.5 cm2) and L-MFC (the electrode anode size is 77.67 cm2), with the external resistor was 300Ω, were 0.23mW/cm2 and 0.41mW/cm2, respectively. In the period of 0~400 h operation, the S-MFC reached the maximum voltage 71.5 mV in 308 hours with the maximum current 186.2 μA, while the L-MFC reached the maximum voltage 97.9 mV in 184 hours with the current 271.3 μA. Moreover, the anode solution COD removal of S-MFC ranged from 1.66% to 6.87% using Ag+ solution as the cathode and the anode solution COD removal in the L-MFC varied from 7.21% to 14.86%.