Natural micro-flora of Palm Oil Mill Effluent (POME) sludge was grown in dual-chamber Microbial Fuel Cells (MFC) to produce electricity by providing glucose at different concentration. A greater strength of Open Circuit Voltage (OCV) was observed with optimal biomass metabolism activity, as increasing glucose concentrations. The time Response Constant (RC) of OCV was taken everyday to estimate the total time needed to achieve steady state voltage at zero current. The lower value of RC indicates that the strength of OCV value is high and the biomass attached to the anode could be active in producing electrons. At 3 750 mg-COD L-1 with 10% added POME and 10 000 mg-COD L-1 synthetic wastewater, the values of RC for each medium were found as 3.36 and 1.95 h, respectively. The removal efficiency of COD was achieved 72.2% for 10% POME and 89.9% for synthetic wastewater. The initial COD level was found proportionally to the COD removal and maximum power density in the MFC system. However, the results shown that relation between RC value and initial COD level were inversely proportional. The highest power density (with present current density) in POME added and synthetic medium were 3.155 mW m-2 (9.322 mA m-2) and 1.780 mW m-2 (3.996 mA m-2), respectively. The optimal power density that conducted in different level of COD was occurred at day 2 before its start decrease at next consecutive day. The effects of electrochemical parameters to power densities at different initial COD level were also studied using polarization model. From the simulated data, averaged power densities (with present current densities) that could achieved at COD 3750 and 10000 mg L-1 were estimated 2.61 mW m-2 (4.5 and 1.38 mA m-2 (3.5 mA m-2)), respectively. The total losses due to current limitation were eliminated about 15-55 % at high initial COD level based on results mention above. The end of study showed that the maximum power density kept on increased although COD value had reached to the lower level and this could be due to the hydrolysis of inactive of the living cells undergone lysis, has contributed to COD level in the system.