Abstract: The application of supercritical Rankine cycle iscommon in order to improve the energetic efficiency of thermal power plants,but due to the low temperature of the gas turbine exhaust outlet, theutilization of supercritical steam cycle as a bottoming cycle in combinedcycles is not possible. Therefore, to achieve a higher efficiency, water asworking fluid of the cycle, should be replaced with another fluid with a lowercritical temperature. For this purpose, water and ammonia mixture (Kalinacycle) has been selected as the bottoming cycle in this manuscript. Unlike thepure water, the mixture of water and ammonia does not evaporate in a constanttemperature, which reduces the evaporator's exergy lost in the heat transferprocess. The energetic efficiency of a supercritical Kalina cycle equipped withan over atmospheric condenser, under thermodynamic conditions of 515 oCand 165 Bar for the gas turbine, ammonia mass fraction are 30% and 70% forcondenser and boiler which is 12% more than Rankine cycle efficiency in the sameconditions. This article is dedicated to modeling and thermodynamic analysis ofa Kalina cycle and introduction of thermo-physical properties of the water andammonia mixture in process of evaporation and condensation. In addition, theperformance comparison of the Kalina cycle and Rankine cycle in terms ofdifferent thermodynamic conditions is issued in this paper.