This paper shows that inlet humidity condition at cathode side is one of dominant parameters affecting the performance of PEMFC. To investigate effects of inlet humidity condition, the performance measurements were conducted for a single PEMFC with two operating variables: cathode relative humidity and dry condition in anode dry. The fuel cell employed for the experiments is a unit PEMFC with a 25, Nafion 112 membrane. As a result of this study, the cell performance is getting higher by increasing inlet humidity condition at cathode side. The cell performance is different from each operating temperature an it has maximum30% higher than dry condition at 60 operating temperature with 80% relative humidity.