Abstarct: Gas turbines are one of the power machines that have many applications in various industries, including power plants, refineries, oil and gas industries. Since a large percentage of the country's energy requirements, is provided in the gas turnibe power plants and also due to the energy requirements of the plants are fossil fuels, Therefore, energy optimization and performance improvement in these power plants is very important. The main purpose of this study is the energy and exergy analysis and improving the efficiency and performance of gas turbine studied. Gas cycle studied in this thesis is related to the Qom power plant. Qom gas turbine power plant consists of four gas units manufactured by Mitsubishi Japan Model MW-701D that each one has a nominal capacity of 128.5 MW and the total 514 MW. In the present thesis, After modeling the Gas cycle and combined cycle by ThermoFlow software, Energy and Exergy analysis of gas cycle are discussed. In the following, the effect of change environmental conditions and levels of the gas turbine load on the gas cycle and power plant will be checked. Then to technical and economic evaluation using three types of system of cooling air inlet to the compressor in the hot six months has been and impact of their use on the gas cycle are studied and finally, with regard to the technical and economic conditions and climatic conditions Qom, fag cooling system as a system for performance improvement at the this power plant is selected and introduced. By using of Fog system in Qom plant, the net power output of the cycle gas and plant, respectively %11.5 and %8.08, energy and exergy efficiency of the cycle gas and plant, respectively %3.64 and %3.6 will be increased and the amount of air pollution by %0.77 will be reduced. In the following, two-objective optimization cycle gas power plant in Qom by a Genetic Algorithm using MATLAB code and in the cold months of the year are paid. Objective functions, the exergy efficiency and the gas cycle costs include maintenance costs, fuel costs and the cost of exergy destruction is. The results show that increasing the exergy efficiency of the gas cycle will also increase costs.