The contribution of solar thermal power to improve the performance of gas-fired combined cycles in very hot and dry environmental conditions is analyzed in this work, The aim of this paper is to study the thermodynamic performance of a proposed integrated solar parabolic trough in which solar field integrated to the bottoming steam cycle of a Combined Cycle Gas Turbine (CCGT) power plant analyzed in three distinct position such as economizer, evaporator and super-heater. Although the analysis is aimed to studying such complementary effects in the widest perspective the cycle simulated and validated Qom combine cycle power plant in Iran with hot and dry climate. In-house code generated to calculate exergy in different locations of plant and also HRSG. Results indicate that Using solar field as economizer, evaporator and super heater increased the net output work about 2.7 MW, 5.47 MW and 7.58 MW respectively and decreases energy efficiencies about 0.61%, 0.25% and 0.17% respectively for the same area of solar field. Also exergy analysis indicates that, using solar cycle as economizer, evaporator and super heater having cycle exergy efficiency of 85.7%, 85.6% and 86% respectively. Evaluated results indicate that using solar plant as super heater having highest energy and exergy efficiency and power output in contrast to other locations, as conclusion this paper suggests using solar plants as super heater offers highest efficiency and power in overall.