The cathodic catalyst plays an important role in the electricity generation of the microbial fuel cell (MFC). In order to evaluate the efficiency of oxygen reduction on the carbon nanotube (CNT) functionalized with different carboxylic groups supported Pt, carboxylic CNTs under the conditions of 80 degrees C and 95 degrees C were prepared, respectively. Pt/CNT catalysts (Pt/CNT-80 and Pt/CNT-95) was prepared by the dipping-precipitation method and their oxygen reduction efficiency was tested in the MFC (MFC-80, MFC-95 and MFC-C) with the air cathode. The results showed that the maximum power output densities of the MFC-95 and MFC-80 were 568.8 mWx m(-2) and 412.8 mWx m(-2), internal resistances were 204.7 omega and 207.7 omega, and open circuit potentials were 0.719 V and 0.651 V, respectively. However, the maximum power output density of the control MFC-C was only 5.4 mW x m(-2), and its internal resistance was 826.2 omega. XPS and XRD analysis results demonstrate that the efficiency of Pt/CNT-95 catalyst is better than Pt/CNT-80 may result from the surface of carboxylic CNT in the 95 degrees C introduced rich oxygen containing groups.