Microfluidic fuel cells are a group of miniaturized fuel cells without membranes for operation. Their unique flow of the steams in a microchannel allows a parallel laminar flow without mixing with each other. We investigated the cell performance with different iron-based soluble salts as oxidants. The best performance was achieved by FeCl3 as the oxidant, achieving the highest power density of 192.71 mW cm(-3) and the largest limiting current density of 883.33 mA cm(-3) (normalized to the active electrode volume). And we optimized the performance of the FeCl3-based microfluidic fuel cell by adjusting the flow rates, HCl concentrations, and FeCl3 concentrations. The optimal flow rate was 20 mL h(-1). Although the maximum power density of the cell with 4 M HCl and 0.5 M FeCl3 solution reached high values of 212.21 mW cm(-3) and 250.42 mW cm(-3), respectively, both cell performances were under mass transfer control at high current densities.