Utilizing oxygen with methane as fuel is a feasible reforming strategy, more convenient and less costly in terms of configuration in solid oxide fuel cells (SOFC) systems. Current study addresses the issues related to the favorable operating conditions for the internal catalytic partial oxidation (CPOX) reforming of methane over Ni-YSZ cermet anode of SOFCs with a new analytical approach on the basis of Reynolds number (Re). The effect of the different flow rates of methane-oxygen mixed gas on the performances of SOFC are studied in fixed methane to oxygen ratio. The results indicated thatthe peak of power density (PPD) strongly depends upon the Reynolds number at the fuel channel inlet that controls the mixture of methane and air mass flow rate. The maximum value of PPD is obtained in Reynolds 10 and also the PPD is decreased by increasing Re. The electrochemical experiment showed stable performance of the SOFC in this condition and confirmed its durability after 120 h testing. The electron microscopy demonstrated that there is no trace of carbon in the anode which led to the durability of the SOFCs.