Abstarct: Gas turbines are today one of the power machines that have many applications in various industries, including power plants, refineries, petrochemicals, oil and gas industries. Gas turbine manufacturers predicted turbine operating conditions in ISO ambient conditions. however, mainly gas turbines are used in other than ISO conditions. Predicted turbine performance, especially in off-design conditions is important. Studies show that change in environmental conditions and changes in load of the turbine can cause a dramatic shift in the gas turbine performance so that understanding of how changes in the quality and performance of the turbine can be very effective. This is important when we want to changes in air conditions or in some parts of the turbine in order to improve the performance of gas turbine. because the main technical and economic evaluation of such projects is prediction of gas turbine performance improvement while conditions is changed. Performance analysis of power production systems from the perspective of the second law of thermodynamics and exergy analysis is one of the newest works in the field of energy conversion. Coupled this tool with analytical tools that use the first law of thermodynamics in the baxse can lead to exact analysis of a power generation system. It seems, developing a model and simulator program with simplicity, low cost and high accuracy and so use of newest tools to analyze quantity and quality of the systems energy conversion in different environmental conditions and different load, can be highly efficient and useful to prediction performance of gas turbines. In the present thesis, is to study the works done and the latest researches in the field of gas turbine performance simulation, especially in the off-design and part-load conditions using thermodynamic relations and factor of turbine load control, in relations. gas turbine performance will be simulated at various load frequency…