This study evaluated the performance characteristics of a molten carbonate fuel cell (MCFC) under sulfur poisoning condition. A 100 cm2 bench-scale MCFC was used for the performance test. The performance of the cell at the normal operation condition was measured at 620 °C under atmospheric pressure. To evaluate the sulfur poisoning effect, 50 ppm H2S/Balanced N2 gas mixture at a flow rate of 30 ml/min was injected into the anode. The cell performance was analyzed via steady-state polarization (SSP) and inert gas step addition (ISA) methods. The overpotential of the cell was observed to have been changed by the injection of H2S gas, and an overpotential increase of ca. 40% was recorded after about 100 hours from the point of addition of the H2S gas. A voltage reduction rate of - 2.62X10-4 mV/s was recorded at a current density of 150mA/cm2 after about 240 hours. The steady-state polarization characteristics of the cell showed that the sulfur poisoning was relatively slow. In addition, the effect of H2S gas on the cell performance was quantitatively measured by the ISA method.