The humidification system in a PEFC is handicapped by the water management under a range of temperatures including low temperatures in winter, so the performance with and without humidification was considered and simulated for a variety of fuel cell temperatures. The characteristice of a single cell with a cell area of 104 cm² was identified by experiments and a one dimensional model was developed to evaluate cell performance. The experiments found that water managements are important because the ionic conductivity of the membrane and catalyst layers decreases when there is little humidity. Results of start-up tests with the cell showed that the fuel cell recover the performance quickly in temperature as low as 10°C. The one dimensional simulation model showed that the measured cell performance agrees with the modeling results for various humidity conditions of the cell. If low reaction temperatures and low current densities are selected as operating conditions, it would be possible to apply the dry system at the start-up.