Fogging system is used as a method for cooling the inlet air to the compressorby the direct injection of water, in order to reduce the ambient air temperatureuntil it reaches the wet bulb temperature and thus increasing the net power.The effects of ambient temperature, relative humidity, firing temperature, and pressureratio on the open cycle gas turbine performance are studied. The ambient temperaturerange, which is considered in this study, ranged from (10 to 60°C); the relative humidityrange was (10% to 90%), the pressure ratio range was (3 to 23) and the firing temperatureswere 1100K, 1200K, 1400K, and 1600K. The results of this study showed that outputpower and efficiency increase continuously with increasing the firing temperature, andreduces with increasing the ambient temperature, and the efficiency increases withpressure ratio reaching a maximum value then it begins reducing. When the relativehumidity increases it is gives a reverse effect on the power and efficiency of this cycle.The present work reveals that using fogging system in the front of the compressor inthe open cycle gas turbine can improve the efficiency and enhance the output power of the cycle due to reducing the inlet air temperature interring to the compressor