In this paper it was dealt with optimization of micro gas turbine with natural gas fuel in four configurations of simple, with regenerator, combined heat and power (CHP) and CHP with regenerator. Target function included energy and exergy efficiencies and electricity cost by considering effects of environmental pollution. Optimization procedures were genetic, bee colony and searching algorithms. Results showed that optimum air fuel ratio calculated by searching method for micro gas turbine with above-mentioned cycles were 1.7, 1.3, 1.6 and 2.3 respectively. By applying Genetic algorithm, optimum air fuel ratios were 1.40, 1.21, 1.42 and 1.82 respectively. At these points, energy efficiency obtained as 29, 34.4, 39.4 and 38.2 %, second law efficiency obtained as 61.4, 74.9, 85.4 and 57.2 %, electricity cost obtained as 0.102, 0.086, 0.075 and 0.029 US$/kWh respectively. By using bee colony algorithm, optimum air fuel ratios were 1.36, 1.13, 1.32 and 1.61 respectively. At these points, energy efficiency are 28.2, 34.3, 40.5 and 35.6 %, second law efficiency are 60.9, 75.67, 81.80 and 56.65 %, electricity costs are 0.105, 0.087, 0.073 and 0.03 US$/kWh respectively. Among these methods, Genetic algorithm was selected as best method because of best answer in optimization.