This paper describes the development of a microbial fuel cell (MFC) for electricity production from cellulose that is based on mixed culture of rumen bacteria in vitro. The fibrolytic bacteria isolated from rumen fluid were used in anode compartment of MFC, which can release glucose up to 15 g/L from carboxymethyl cellulose (CMC). At the same time, the maximum power density of 100.60mWm−2 was generated when using copper sulfate as the cathodic electron acceptor. But the output voltage and current quickly fell down to 0.12 V and 0 mA after 48 h for electrode corroded and toxicity. When using methanogens isolated from the same rumen fluid instead of copper sulfate, the maximum power density about 3090 mWm-2 was recovered. This study demonstrates that symbiotic microorganisms could be used as catalysts and mediators effectively in the cathode for a MFC. CMC concentrations were further found to be the major factor on the output voltage and Coulombic efficiencies.