NOVELTY - A modified carbon based composite anode material preparation method involves purifying a multi-wall carbon nanotube, and placing the carbon nanotube into supporting electrolyte solution. The carbon nanotube in the solution is dispersed with the carbon nanotube. 3,4-Ethylenedioxythiophene monomer is added to the solution to obtain a well-dispersed 3,4-ethylenedioxythiophene/multi-wall carbon nanotube suspending solution followed by depositing a complex on an anode surface to form a layer of a conductive film modified electrode that is vacuum dried and washed to obtain finished product.    USE - Method for preparing modified carbon based composite anode material for microbial fuel cell, such as anaerobic fluidized bed air-cathode microbial fuel cell (claimed).    ADVANTAGE - The method enables preparing composite anode material with peculiar surface effect, better conductivity and electrochemical activity, without toxic reactants, in a cost-effective manner. The material improves power density and open-circuit voltage to the maximum, and reduces internal resistance of a battery.    DETAILED DESCRIPTION - A modified carbon based composite anode material preparation method involves purifying a multi-wall carbon nanotube and placing the purified multi-wall carbon nanotube in 0.1-0.5mol/l of supporting electrolyte solution. The carbon nanotube in the solution is dispersed with carbon nanotube (5-20%) and ultrasonic treatment is performed for 15-30 minutes, where the supporting electrolyte solution comprises sulfate, nitrate or perchlorate. 3,4-Ethylenedioxythiophene monomer (0.01-0.02 mol/l) is added to the solution, and ultrasonic treatment is performed for 4-6 hours to obtain a well-dispersed 3,4-ethylenedioxythiophene/multi-wall carbon nanotube suspending solution followed by electrically depositing a complex on an anode surface by using cyclic voltammetry to form a layer of a conductive film modified electrode. The electrode is vacuum dried and washed with deionized water to remove the impurity on the surface of the electrode and dried to obtain a finished product.