Abstract: The performance of microfluidic-based fuel cells was predicted numerically by Fluent, where liquid fuel and liquid oxidant flow side by side in a channel at microscale and the current of electricity is achieved by electrochemical reactions at electrodes on channel walls. The obtained polarization curves were found to be in good agreement with experiments, and with the increase in the volumetric flow rate, the cell performance rises gradually. In our case, the cell performance is very sensitive to the content of oxygen in the cathode stream, while it is insensitive to the concentration of formic acid in the anode stream, confirming the cathode limited performance in microfluidic fuel cell as reported by others.