A critical issue concerning the gas turbine cycle of combined cycle power station is the reduction in net power output considerably with increasing ambient air temperature. The present simulation study aims to improve the performance of gas turbine cycle of combined cycle power station through use the fresh air handling units of mechanical chiller. To obtains the influence of use the mechanical chiller as pre-cooling units on a performance of gas turbine cycle, the thermodynamic analysis are used to simulate the performance of gas turbine cycle for three different operating loads (66.67, 83.33, and 100% full load). Based on results of the simulation analysis, the mechanical chiller which is inserted as a pre-cooling unit can; (i) increase the average monthly net power output by values varying between 7.33-18.17 MW compared to the original case without pre-cooling units; (ii) the rate of improvement in the average monthly net power output varies between 4.6-11% compared to the case without pre-cooling units; (iii) reduce the specific fuel consumption (SFC) by a rate varying between 5.21-10.81 kgfuel /MWh compared to the original case without pre-cooling units; and (iv) the saving in SFC reached to 4.4% compared to the original case without pre-cooling units.