The present study established the two-dimensional axisymmetric model for a freestanding circular cell of the low-temperature micro-solid oxide fuel cell (mu-SOFC) that is composed of platinum (Pt) electrodes and a yttria-stabilized zirconia (YSZ) electrolyte. The only membrane electrode assembly (MEA) was constructed for the numerical simulation in order to avoid the meshing problem with a very high aspect ratio of the submicron layers. We considered the charge and species conservation equations and electrode kinetics to elucidate the intricate phenomena inside the mu-SOFC. The extensive numerical simulations were carried out by using the commercial code to predict the effect of operating temperature and electrolyte thickness on the electrochemical performance of mu-SOFC. Our numerical model was calibrated with the results from experiments, and we provided the average cell current density and overpotentials with respect to the electrolyte thickness and the operating temperature. It was found that the electrochemical performance increased with the increase in operating temperature, owing to both rapid electrochemical reactions and ionic conduction, even in mu-SOFC. Moreover, the major voltage loss of mu-SOFC at low-temperature was caused by the cathodic activation overpotential.