An air-cathode microbial fuel cell (ACMFC) was successfully started up using anaerobic activated sludge as inoculums, generating a voltage of 0.24V after inoculations for 110 h. When using acetate and glucose as substrate, voltage of 0.38V and 0.41V (based on external resistance of 1000 omega) is obtained; meanwhile, the maximum power density reaches 146.56 mW/m2 and 192.04 mW/m2 respectively, suggesting that organic wastewater can be used to produce electricity. Removal efficiency of 99% (acetate) and 87% (glucose) is achieved simultaneously, demonstrating that ACMFC can treat organic wastewater. Electron recovery efficiency as low as 10% for both acetate and glucose is observed mainly due to aerobic respiration of microorganisms caused by diffusion of oxygen molecular from the cathode, leading to electron loss. MFCs are capable of converting chemical energy presented in organic wastewater into electricity energy with accomplishments of wastewater treatments simultaneously, which possibly captures considerable benefits in terms of environments and economics.