To evaluate the effects of H2S on the performance of molten carbonate fuel cells, bench-scale cell tests were performed and the meniscus heights of the electrolyte on Ni were measured with fuel gases containing various amounts of H2S. In bench-scale cell tests, H2S in the fuel gas had a large effect on cell voltage in the early operating stages, but this effect showed a tendency to decrease with operating time. Basic wetting property measurements revealed that Ni becomes better wetted at higher H2S concentrations. In calculations of the electrolyte distributions, the electrolyte fill of the anode with H2S was found to be higher than that without H2S. This study simulates the electrolyte distributions taking into account the effects of H2S levels, the electrolyte loss and the change in pore size distributions of the electrodes, and discusses the relation between electrolyte distribution and cell performance.